javascript - 代码信号上的常见字符计数挑战

Question

当我遍历两个数组时，大多数测试都通过了。其中一个测试会产生一个问题，因为即使删除了匹配的元素，嵌套循环也会继续针对第一个循环。

输入：s1：“abca” s2：“xyzbac”

这是我的代码：

function commonCharacterCount(s1, s2) {
    const arrayOne = s1.split("")
    const arrayTwo = s2.split("")
    var matches = [];

    for (let i = 0; i < arrayOne.length; i++) {
        for (let j = 0; j < arrayTwo.length; j++) {
            console.log(arrayTwo[j],arrayOne[i], matches)
           if (arrayOne[i] === arrayTwo[j]) {
               matches.push(arrayOne[i])
               arrayOne.splice(arrayOne[i], 1)
        
           }
        }
    }
    return matches.length
}

我检查了测试 3 上的控制台日志，这是唯一失败的日志，我可以看到跳过第二项“b”时出现问题。

标签： javascriptarraysloops

Answer 1

Since you are slicing arrayOne you remove an item from arrayOne and this means that it will skip over an item because the variable i gets incremented by 1 but the arrayOne loses an item. So you get something like this.

arrayOne = ["a","b","c","d"]  
i = 0  
arrayOne[i] results to "a"

now you find a match with arrayTwo and you slice arrayOne at the index i of your match so arrayOne becomes

arrayOne = ["b","c","d"]  
//however you still increment i by one so i becomes  
i = 1  
//so now arrayOne[i] becomes  
arrayOne[i] results to "c"

Now I'm not sure my explanation is any good but I have two solutions. 1 doesn't splice and the other does but when it does it decrements i by one.

option 1

function commonCharacterCount(s1, s2) {
    const arrayOne = s1.split("")
    const arrayTwo = s2.split("")
    var matches = [];

    for (let i = 0; i < arrayOne.length; i++) {
        for (let j = 0; j < arrayTwo.length; j++) {
            console.log(arrayTwo[j],arrayOne[i], matches)
           if (arrayOne[i] === arrayTwo[j]) {
               matches.push(arrayOne[i])        
           }
        }
    }
    return matches.length
}

option 2

function commonCharacterCount(s1, s2) {
    const arrayOne = s1.split("")
    const arrayTwo = s2.split("")
    var matches = [];

    for (let i = 0; i < arrayOne.length; i++) {
        for (let j = 0; j < arrayTwo.length; j++) {
            console.log(arrayTwo[j],arrayOne[i], matches)
           if (arrayOne[i] === arrayTwo[j]) {
               matches.push(arrayOne[i])
               arrayOne.splice(arrayOne[i], 1)
               i--
           }
        }
    }
    return matches.length
}