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pwnable.kr-balckjack-Writeup
该题的代码奇长无比（788行）但题挺容易，并且比较有意思
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首先从提供的网址https://cboard.cprogramming.com/c-programming/114023-simple-blackjack-program.html查看该题用到的代码如下：
View Code1 // Programmer: Vladislav Shulman 2 // Final Project 3 // Blackjack 4 5 // Feel free to use any and all parts of this program and claim it as your own work 6 7 //FINAL DRAFT 8 9 #include <stdlib.h> 10 #include <stdio.h> 11 #include <math.h> 12 #include <time.h> //Used for srand((unsigned) time(NULL)) command 13 #include <process.h> //Used for system("cls") command 14 15 #define spade 06 //Used to print spade symbol 16 #define club 05 //Used to print club symbol 17 #define diamond 04 //Used to print diamond symbol 18 #define heart 03 //Used to print heart symbol 19 #define RESULTS "Blackjack.txt" //File name is Blackjack 20 21 //Global Variables 22 int k; 23 int l; 24 int d; 25 int won; 26 int loss; 27 int cash = 500; 28 int bet; 29 int random_card; 30 int player_total=0; 31 int dealer_total; 32 33 //Function Prototypes 34 int clubcard(); //Displays Club Card Image 35 int diamondcard(); //Displays Diamond Card Image 36 int heartcard(); //Displays Heart Card Image 37 int spadecard(); //Displays Spade Card Image 38 int randcard(); //Generates random card 39 int betting(); //Asks user amount to bet 40 void asktitle(); //Asks user to continue 41 void rules(); //Prints "Rules of Vlad's Blackjack" menu 42 void play(); //Plays game 43 void dealer(); //Function to play for dealer AI 44 void stay(); //Function for when user selects 'Stay' 45 void cash_test(); //Test for if user has cash remaining in purse 46 void askover(); //Asks if user wants to continue playing 47 void fileresults(); //Prints results into Blackjack.txt file in program directory 48 49 //Main Function 50 int main(void) 51 { 52 int choice1; 53 printf(" "); 54 printf(" "); 55 printf(" "); 56 printf(" 222 111 "); 57 printf(" 222 222 11111 "); 58 printf(" 222 222 11 111 "); 59 printf(" 222 111 "); 60 printf(" 222 111 "); 61 printf(" "); 62 printf(" %c%c%c%c%c %c%c %c%c %c%c%c%c%c %c %c ", club, club, club, club, club, spade, spade, diamond, diamond, heart, heart, heart, heart, heart, club, club); 63 printf(" %c %c %c%c %c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, heart, club, club); 64 printf(" %c %c %c%c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, club, club); 65 printf(" %c%c%c%c%c %c%c %c %c%c %c %c %c %c ", club, club, club, club, club, spade, spade, diamond, diamond, diamond, diamond, heart, club, club); 66 printf(" %c %c %c%c %c %c%c%c%c %c %c %c%c %c ", club, club, spade, spade, diamond, diamond, diamond, diamond, diamond, diamond, heart, club, club, club); 67 printf(" %c %c %c%c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, club, club); 68 printf(" %c %c %c%c %c %c %c %c %c %c ", club, club, spade, spade, diamond, diamond, heart, heart, club, club); 69 printf(" %c%c%c%c%c%c %c%c%c%c%c%c%c %c %c %c%c%c%c%c %c %c ", club, club, club, club, club, club, spade, spade, spade, spade, spade, spade, spade, diamond, diamond, heart, heart, heart, heart, heart, club, club); 70 printf(" "); 71 printf(" 21 "); 72 73 printf(" %c%c%c%c%c%c%c%c %c%c %c%c%c%c%c %c %c ", diamond, diamond, diamond, diamond, diamond, diamond, diamond, diamond, heart, heart, club, club, club, club, club, spade, spade); 74 printf(" %c%c %c %c %c %c %c %c ", diamond, diamond, heart, heart, club, club, spade, spade); 75 printf(" %c%c %c %c %c %c %c ", diamond, diamond, heart, heart, club, spade, spade); 76 printf(" %c%c %c %c%c %c %c %c %c ", diamond, diamond, heart, heart, heart, heart, club, spade, spade); 77 printf(" %c%c %c %c%c%c%c %c %c %c%c %c ", diamond, diamond, heart, heart, heart, heart, heart, heart, club, spade, spade, spade); 78 printf(" %c%c %c %c %c %c %c ", diamond, diamond, heart, heart, club, spade, spade); 79 printf(" %c %c%c %c %c %c %c %c %c ", diamond, diamond, diamond, heart, heart, club, spade, spade); 80 printf(" %c%c%c %c %c %c%c%c%c%c %c %c ", diamond, diamond, diamond, heart, heart, club, club, club, club, club, spade, spade); 81 printf(" "); 82 printf(" 222 111 "); 83 printf(" 222 111 "); 84 printf(" 222 111 "); 85 printf(" 222222222222222 111111111111111 "); 86 printf(" 2222222222222222 11111111111111111 "); 87 printf(" "); 88 printf(" "); 89 90 asktitle(); 91 92 printf(" "); 93 printf(" "); 94 system("pause"); 95 return(0); 96 } //end program 97 98 void asktitle() // Function for asking player if they want to continue 99 { 100 char choice1; 101 int choice2; 102 103 printf(" Are You Ready?"); 104 printf(" ----------------"); 105 printf(" (Y/N) "); 106 scanf(" %c",&choice1); 107 108 while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered 109 { 110 printf(" "); 111 printf("Incorrect Choice. Please Enter Y for Yes or N for No. "); 112 scanf("%c",&choice1); 113 } 114 115 116 if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. Prints menu. 117 { 118 system("cls"); 119 printf(" Enter 1 to Begin the Greatest Game Ever Played."); 120 printf(" Enter 2 to See a Complete Listing of Rules."); 121 printf(" Enter 3 to Exit Game. (Not Recommended)"); 122 printf(" Choice: "); 123 scanf("%d", &choice2); // Prompts user for choice 124 if((choice2<1) || (choice2>3)) // If invalid choice entered 125 { 126 printf(" Incorrect Choice. Please enter 1, 2 or 3 "); 127 scanf("%d", &choice2); 128 } 129 switch(choice2) // Switch case for different choices 130 { 131 case 1: // Case to begin game 132 system("cls"); 133 134 play(); 135 136 break; 137 138 case 2: // Case to see rules 139 system("cls"); 140 rules(); 141 break; 142 143 case 3: // Case to exit game 144 printf(" Your day could have been perfect."); 145 printf(" Have an almost perfect day! "); 146 system("pause"); 147 exit(0); 148 break; 149 150 default: 151 printf(" Invalid Input"); 152 } // End switch case 153 } // End if loop 154 155 156 157 else if((choice1 == 'N') || (choice1 == 'n')) // If no, exit program 158 { 159 printf(" Your day could have been perfect."); 160 printf(" Have an almost perfect day! "); 161 system("pause"); 162 exit(0); 163 } 164 165 return; 166 } // End function 167 168 void rules() //Prints "Rules of Vlad's Blackjack" list 169 { 170 char choice1; 171 int choice2; 172 173 printf(" RULES of VLAD's BLACKJACK"); 174 printf(" ---------------------------"); 175 printf(" I."); 176 printf(" Thou shalt not question the odds of this game."); 177 printf(" %c This program generates cards at random.", spade); 178 printf(" %c If you keep losing, you are very unlucky! ", diamond); 179 180 printf(" II."); 181 printf(" Each card has a value."); 182 printf(" %c Number cards 1 to 10 hold a value of their number.", spade); 183 printf(" %c J, Q, and K cards hold a value of 10.", diamond); 184 printf(" %c Ace cards hold a value of 11", club); 185 printf(" The goal of this game is to reach a card value total of 21. "); 186 187 printf(" III."); 188 printf(" After the dealing of the first two cards, YOU must decide whether to HIT or STAY."); 189 printf(" %c Staying will keep you safe, hitting will add a card.", spade); 190 printf(" Because you are competing against the dealer, you must beat his hand."); 191 printf(" BUT BEWARE!."); 192 printf(" %c If your total goes over 21, you will LOSE!.", diamond); 193 printf(" But the world is not over, because you can always play again. "); 194 printf(" %c%c%c YOUR RESULTS ARE RECORDED AND FOUND IN SAME FOLDER AS PROGRAM %c%c%c ", spade, heart, club, club, heart, spade); 195 printf(" Would you like to go the previous screen? (I will not take NO for an answer)"); 196 printf(" (Y/N) "); 197 scanf(" %c",&choice1); 198 199 while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered 200 { 201 printf(" "); 202 printf("Incorrect Choice. Please Enter Y for Yes or N for No. "); 203 scanf("%c",&choice1); 204 } 205 206 207 if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. Prints menu. 208 { 209 system("cls"); 210 asktitle(); 211 } // End if loop 212 213 214 215 else if((choice1 == 'N') || (choice1 == 'n')) // If no, convinces user to enter yes 216 { 217 system("cls"); 218 printf(" I told you so. "); 219 asktitle(); 220 } 221 222 return; 223 } // End function 224 225 int clubcard() //Displays Club Card Image 226 { 227 228 229 srand((unsigned) time(NULL)); //Generates random seed for rand() function 230 k=rand()%13+1; 231 232 if(k<=9) //If random number is 9 or less, print card with that number 233 { 234 //Club Card 235 printf("------- "); 236 printf("|%c | ", club); 237 printf("| %d | ", k); 238 printf("| %c| ", club); 239 printf("------- "); 240 } 241 242 243 if(k==10) //If random number is 10, print card with J (Jack) on face 244 { 245 //Club Card 246 printf("------- "); 247 printf("|%c | ", club); 248 printf("| J | "); 249 printf("| %c| ", club); 250 printf("------- "); 251 } 252 253 254 if(k==11) //If random number is 11, print card with A (Ace) on face 255 { 256 //Club Card 257 printf("------- "); 258 printf("|%c | ", club); 259 printf("| A | "); 260 printf("| %c| ", club); 261 printf("------- "); 262 if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total 263 { 264 k=11; 265 } 266 267 else 268 { 269 270 k=1; 271 } 272 } 273 274 275 if(k==12) //If random number is 12, print card with Q (Queen) on face 276 { 277 //Club Card 278 printf("------- "); 279 printf("|%c | ", club); 280 printf("| Q | "); 281 printf("| %c| ", club); 282 printf("------- "); 283 k=10; //Set card value to 10 284 } 285 286 287 if(k==13) //If random number is 13, print card with K (King) on face 288 { 289 //Club Card 290 printf("------- "); 291 printf("|%c | ", club); 292 printf("| K | "); 293 printf("| %c| ", club); 294 printf("------- "); 295 k=10; //Set card value to 10 296 } 297 return k; 298 }// End function 299 300 int diamondcard() //Displays Diamond Card Image 301 { 302 303 304 srand((unsigned) time(NULL)); //Generates random seed for rand() function 305 k=rand()%13+1; 306 307 if(k<=9) //If random number is 9 or less, print card with that number 308 { 309 //Diamond Card 310 printf("------- "); 311 printf("|%c | ", diamond); 312 printf("| %d | ", k); 313 printf("| %c| ", diamond); 314 printf("------- "); 315 } 316 317 if(k==10) //If random number is 10, print card with J (Jack) on face 318 { 319 //Diamond Card 320 printf("------- "); 321 printf("|%c | ", diamond); 322 printf("| J | "); 323 printf("| %c| ", diamond); 324 printf("------- "); 325 } 326 327 if(k==11) //If random number is 11, print card with A (Ace) on face 328 { 329 //Diamond Card 330 printf("------- "); 331 printf("|%c | ", diamond); 332 printf("| A | "); 333 printf("| %c| ", diamond); 334 printf("------- "); 335 if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total 336 { 337 k=11; 338 } 339 340 else 341 { 342 k=1; 343 } 344 } 345 346 if(k==12) //If random number is 12, print card with Q (Queen) on face 347 { 348 //Diamond Card 349 printf("------- "); 350 printf("|%c | ", diamond); 351 printf("| Q | "); 352 printf("| %c| ", diamond); 353 printf("------- "); 354 k=10; //Set card value to 10 355 } 356 357 if(k==13) //If random number is 13, print card with K (King) on face 358 { 359 //Diamond Card 360 printf("------- "); 361 printf("|%c | ", diamond); 362 printf("| K | "); 363 printf("| %c| ", diamond); 364 printf("------- "); 365 k=10; //Set card value to 10 366 } 367 return k; 368 }// End function 369 370 int heartcard() //Displays Heart Card Image 371 { 372 373 374 srand((unsigned) time(NULL)); //Generates random seed for rand() function 375 k=rand()%13+1; 376 377 if(k<=9) //If random number is 9 or less, print card with that number 378 { 379 //Heart Card 380 printf("------- "); 381 printf("|%c | ", heart); 382 printf("| %d | ", k); 383 printf("| %c| ", heart); 384 printf("------- "); 385 } 386 387 if(k==10) //If random number is 10, print card with J (Jack) on face 388 { 389 //Heart Card 390 printf("------- "); 391 printf("|%c | ", heart); 392 printf("| J | "); 393 printf("| %c| ", heart); 394 printf("------- "); 395 } 396 397 if(k==11) //If random number is 11, print card with A (Ace) on face 398 { 399 //Heart Card 400 printf("------- "); 401 printf("|%c | ", heart); 402 printf("| A | "); 403 printf("| %c| ", heart); 404 printf("------- "); 405 if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total 406 { 407 k=11; 408 } 409 410 else 411 { 412 k=1; 413 } 414 } 415 416 if(k==12) //If random number is 12, print card with Q (Queen) on face 417 { 418 //Heart Card 419 printf("------- "); 420 printf("|%c | ", heart); 421 printf("| Q | "); 422 printf("| %c| ", heart); 423 printf("------- "); 424 k=10; //Set card value to 10 425 } 426 427 if(k==13) //If random number is 13, print card with K (King) on face 428 { 429 //Heart Card 430 printf("------- "); 431 printf("|%c | ", heart); 432 printf("| K | "); 433 printf("| %c| ", heart); 434 printf("------- "); 435 k=10; //Set card value to 10 436 } 437 return k; 438 } // End Function 439 440 int spadecard() //Displays Spade Card Image 441 { 442 443 444 srand((unsigned) time(NULL)); //Generates random seed for rand() function 445 k=rand()%13+1; 446 447 if(k<=9) //If random number is 9 or less, print card with that number 448 { 449 //Spade Card 450 printf("------- "); 451 printf("|%c | ", spade); 452 printf("| %d | ", k); 453 printf("| %c| ", spade); 454 printf("------- "); 455 } 456 457 if(k==10) //If random number is 10, print card with J (Jack) on face 458 { 459 //Spade Card 460 printf("------- "); 461 printf("|%c | ", spade); 462 printf("| J | "); 463 printf("| %c| ", spade); 464 printf("------- "); 465 } 466 467 if(k==11) //If random number is 11, print card with A (Ace) on face 468 { 469 //Spade Card 470 printf("------- "); 471 printf("|%c | ", spade); 472 printf("| A | "); 473 printf("| %c| ", spade); 474 printf("------- "); 475 if(player_total<=10) //If random number is Ace, change value to 11 or 1 depending on dealer total 476 { 477 k=11; 478 } 479 480 else 481 { 482 k=1; 483 } 484 } 485 486 if(k==12) //If random number is 12, print card with Q (Queen) on face 487 { 488 //Spade Card 489 printf("------- "); 490 printf("|%c | ", spade); 491 printf("| Q | "); 492 printf("| %c| ", spade); 493 printf("------- "); 494 k=10; //Set card value to 10 495 } 496 497 if(k==13) //If random number is 13, print card with K (King) on face 498 { 499 //Spade Card 500 printf("------- "); 501 printf("|%c | ", spade); 502 printf("| K | "); 503 printf("| %c| ", spade); 504 printf("------- "); 505 k=10; //Set card value to 10 506 } 507 return k; 508 } // End Function 509 510 int randcard() //Generates random card 511 { 512 513 514 srand((unsigned) time(NULL)); //Generates random seed for rand() function 515 random_card = rand()%4+1; 516 517 if(random_card==1) 518 { 519 clubcard(); 520 l=k; 521 } 522 523 if(random_card==2) 524 { 525 diamondcard(); 526 l=k; 527 } 528 529 if(random_card==3) 530 { 531 heartcard(); 532 l=k; 533 } 534 535 if(random_card==4) 536 { 537 spadecard(); 538 l=k; 539 } 540 return l; 541 } // End Function 542 543 void play() //Plays game 544 { 545 546 int p=0; // holds value of player_total 547 int i=1; // counter for asking user to hold or stay (aka game turns) 548 char choice3; 549 550 cash = cash; 551 cash_test(); 552 printf(" Cash: $%d ",cash); //Prints amount of cash user has 553 randcard(); //Generates random card 554 player_total = p + l; //Computes player total 555 p = player_total; 556 printf(" Your Total is %d ", p); //Prints player total 557 dealer(); //Computes and prints dealer total 558 betting(); //Prompts user to enter bet amount 559 560 while(i<=21) //While loop used to keep asking user to hit or stay at most twenty-one times 561 // because there is a chance user can generate twenty-one consecutive 1's 562 { 563 if(p==21) //If user total is 21, win 564 { 565 printf(" Unbelievable! You Win! "); 566 won = won+1; 567 cash = cash+bet; 568 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 569 dealer_total=0; 570 askover(); 571 } 572 573 if(p>21) //If player total is over 21, loss 574 { 575 printf(" Woah Buddy, You Went WAY over. "); 576 loss = loss+1; 577 cash = cash - bet; 578 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 579 dealer_total=0; 580 askover(); 581 } 582 583 if(p<=21) //If player total is less than 21, ask to hit or stay 584 { 585 printf(" Would You Like to Hit or Stay?"); 586 587 scanf("%c", &choice3); 588 while((choice3!='H') && (choice3!='h') && (choice3!='S') && (choice3!='s')) // If invalid choice entered 589 { 590 printf(" "); 591 printf("Please Enter H to Hit or S to Stay. "); 592 scanf("%c",&choice3); 593 } 594 595 596 if((choice3=='H') || (choice3=='h')) // If Hit, continues 597 { 598 randcard(); 599 player_total = p + l; 600 p = player_total; 601 printf(" Your Total is %d ", p); 602 dealer(); 603 if(dealer_total==21) //Is dealer total is 21, loss 604 { 605 printf(" Dealer Has the Better Hand. You Lose. "); 606 loss = loss+1; 607 cash = cash - bet; 608 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 609 dealer_total=0; 610 askover(); 611 } 612 613 if(dealer_total>21) //If dealer total is over 21, win 614 { 615 printf(" Dealer Has Went Over!. You Win! "); 616 won = won+1; 617 cash = cash+bet; 618 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 619 dealer_total=0; 620 askover(); 621 } 622 } 623 if((choice3=='S') || (choice3=='s')) // If Stay, does not continue 624 { 625 printf(" You Have Chosen to Stay at %d. Wise Decision! ", player_total); 626 stay(); 627 } 628 } 629 i++; //While player total and dealer total are less than 21, re-do while loop 630 } // End While Loop 631 } // End Function 632 633 void dealer() //Function to play for dealer AI 634 { 635 int z; 636 637 if(dealer_total<17) 638 { 639 srand((unsigned) time(NULL) + 1); //Generates random seed for rand() function 640 z=rand()%13+1; 641 if(z<=10) //If random number generated is 10 or less, keep that value 642 { 643 d=z; 644 645 } 646 647 if(z>11) //If random number generated is more than 11, change value to 10 648 { 649 d=10; 650 } 651 652 if(z==11) //If random number is 11(Ace), change value to 11 or 1 depending on dealer total 653 { 654 if(dealer_total<=10) 655 { 656 d=11; 657 } 658 659 else 660 { 661 d=1; 662 } 663 } 664 dealer_total = dealer_total + d; 665 } 666 667 printf(" The Dealer Has a Total of %d", dealer_total); //Prints dealer total 668 669 } // End Function 670 671 void stay() //Function for when user selects 'Stay' 672 { 673 dealer(); //If stay selected, dealer continues going 674 if(dealer_total>=17) 675 { 676 if(player_total>=dealer_total) //If player's total is more than dealer's total, win 677 { 678 printf(" Unbelievable! You Win! "); 679 won = won+1; 680 cash = cash+bet; 681 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 682 dealer_total=0; 683 askover(); 684 } 685 if(player_total<dealer_total) //If player's total is less than dealer's total, loss 686 { 687 printf(" Dealer Has the Better Hand. You Lose. "); 688 loss = loss+1; 689 cash = cash - bet; 690 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 691 dealer_total=0; 692 askover(); 693 } 694 if(dealer_total>21) //If dealer's total is more than 21, win 695 { 696 printf(" Unbelievable! You Win! "); 697 won = won+1; 698 cash = cash+bet; 699 printf(" You have %d Wins and %d Losses. Awesome! ", won, loss); 700 dealer_total=0; 701 askover(); 702 } 703 } 704 else 705 { 706 stay(); 707 } 708 709 } // End Function 710 711 void cash_test() //Test for if user has cash remaining in purse 712 { 713 if (cash <= 0) //Once user has zero remaining cash, game ends and prompts user to play again 714 { 715 printf("You Are Bankrupt. Game Over"); 716 cash = 500; 717 askover(); 718 } 719 } // End Function 720 721 int betting() //Asks user amount to bet 722 { 723 printf(" Enter Bet: $"); 724 scanf("%d", &bet); 725 726 if (bet > cash) //If player tries to bet more money than player has 727 { 728 printf(" You cannot bet more money than you have."); 729 printf(" Enter Bet: "); 730 scanf("%d", &bet); 731 return bet; 732 } 733 else return bet; 734 } // End Function 735 736 void askover() // Function for asking player if they want to play again 737 { 738 char choice1; 739 740 printf(" Would You Like To Play Again?"); 741 printf(" Please Enter Y for Yes or N for No "); 742 scanf(" %c",&choice1); 743 744 while((choice1!='Y') && (choice1!='y') && (choice1!='N') && (choice1!='n')) // If invalid choice entered 745 { 746 printf(" "); 747 printf("Incorrect Choice. Please Enter Y for Yes or N for No. "); 748 scanf("%c",&choice1); 749 } 750 751 752 if((choice1 == 'Y') || (choice1 == 'y')) // If yes, continue. 753 { 754 system("cls"); 755 play(); 756 } 757 758 else if((choice1 == 'N') || (choice1 == 'n')) // If no, exit program 759 { 760 fileresults(); 761 printf(" BYE!!!! "); 762 system("pause"); 763 exit(0); 764 } 765 return; 766 } // End function 767 768 void fileresults() //Prints results into Blackjack.txt file in program directory 769 { 770 FILE *fpresults; //File pointer is fpresults 771 fpresults = fopen(RESULTS, "w"); //Creates file and writes into it 772 if(fpresults == NULL) // what to do if file missing from directory 773 { 774 printf(" Error: File Missing "); 775 system("pause"); 776 exit(1); 777 } 778 else 779 { 780 fprintf(fpresults," RESULTS"); 781 fprintf(fpresults," --------- "); 782 fprintf(fpresults," You Have Won %d Times ", won); 783 fprintf(fpresults," You Have Lost %d Times ", loss); 784 fprintf(fpresults," Keep Playing and Set an All-Time Record!"); 785 } 786 fclose(fpresults); 787 return; 788 } // End Function
虽然代码足足有近800行，但根据代码的流程逐渐分析，还是能分析出以下信息：
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游戏规则
- 玩家在每轮游戏开始之前设置赌资；
- 玩家的任务是通过hit（继续加扑克牌）或者stay（等待）使自己的点数之和等于21；
- 卡片1~10的点数即为相对应的数字，卡片J，Q，K的点数为10，卡片A的点数为11；
- 当自己的点数大于了21，或者自己的点数小于了庄家的点数，玩家输；则要从赌本中减去赌资；
- 当玩家的点数之和等于21时，玩家胜；玩家就从庄家处赚取同赌资金额的金钱；
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当玩家的赌本大于1000000时，胜利，即可拿到flag；
由以上分析，首先先到了三种方法作弊（或者相信自己的人品无穷大，可以通过自己的努力能成为百万富翁）：
- 直接修改赌本为 ≥ 1000000；
- 通过修改， 使自己每局都能获胜，那么需要
- 在每局结束时动手脚，增加赌本
分析代码，前两种想法没有找到相应的漏洞，
第三种方法，分析betting函数:
1 int betting() //Asks user amount to bet 2 { 3 printf(" Enter Bet: $"); 4 scanf("%d", &bet); 5 6 if (bet > cash) //If player tries to bet more money than player has 7 { 8 printf(" You cannot bet more money than you have."); 9 printf(" Enter Bet: "); 10 scanf("%d", &bet); 11 return bet; 12 } 13 else return bet; 14 } // End Function
- 可以看出函数对输入的赌资只做了是否小于赌本的判断，那么我们就可以输入一个负的大小合适的赌本（大小合适指不会数据溢出），如-1000000；
- 那么，如果我们输掉了那一局，我们的赌本就要减负的1000000，就是加正的1000000，就可以拿到flag；
经过几次探索，拿到flag如下：
则flag即为YaY_I_AM_A_MILLIONARE_LOL
2017-2-16 8:16;47