冒泡排序+二分查找

　　冒泡排序：

<script>
    var flag = false;
    var arr1 = [0,-90,89,36743,87,-89,9]
    for(var i=0;i<arr1.length-1;i++){
        for(var j=0;j<arr1.length-1-i;j++){
            if(arr1[j]>arr1[j+1]){
                var temp = arr1[j];
                arr1[j]=arr1[j+1]
                arr1[j+1]=temp;
                flag=true;
            }
        }
        if(flag){
            flag=false;
        }else{
            break;
        }
    }
    for(var i=0;i<arr1.length;i++){
        document.write(arr1[i]+" ")
    }
</script>

结果：

二分查找：

　　思路：找到数组中间的数（midVal）,和你要查找的数（findVal）进行比较，如果midVal>findVal则说明findVal在数组的左边，就把给数组二分（就只在左边查找）

　　注意：前提条件：改数组必须是一个有序数组

// 非递归算法
        function binary_search(arr, key) {
            var low = 0,
                high = arr.length - 1;
            while(low <= high){
                var mid = parseInt((high + low) / 2);
                if(key == arr[mid]){
                    return  mid;
                }else if(key > arr[mid]){
                    low = mid + 1;
                }else if(key < arr[mid]){
                    high = mid -1;
                }else{
                    return -1;
                }
            }
        };
        var arr = [1,2,3,4,5,6,7,8,9,10,11,23,44,86];
        var result = binary_search(arr,10);
        alert(result); // 9 返回目标元素的索引值       

    // 递归算法
        function binary_search(arr,low, high, key) {
            if (low > high){
                return -1;
            }
            var mid = parseInt((high + low) / 2);
            if(arr[mid] == key){
                return mid;
            }else if (arr[mid] > key){
                high = mid - 1;
                return binary_search(arr, low, high, key);
            }else if (arr[mid] < key){
                low = mid + 1;
                return binary_search(arr, low, high, key);
            }
        };
        var arr = [1,2,3,4,5,6,7,8,9,10,11,23,44,86];
        var result = binary_search(arr, 0, 13, 10);
        alert(result); // 9 返回目标元素的索引值

还可以这样写：
var arr =[1,2,4,5,6,89];
    function binarySearch(arr,findVal,leftIndex,rightIndex){
        //防止无穷递归
        if(leftIndex>rightIndex){
            document.writeln("找不到");
            return ;
        }
        //找到中间这个值
        var midIndex = Math.floor((leftIndex+rightIndex)/2); //floor()是进行下舍入，即3.5就是3，ceil()为上舍入
        console.log(midIndex)
        var midVal = arr[midIndex];
        if(midVal>findVal){
            //在左边找
            binarySearch(arr,findVal,leftIndex,midIndex-1);
        }else if(midVal<findVal){
            //再往右边找
            binarySearch(arr,findVal,midIndex+1,rightIndex);
        }else{
            document.writeln("找到下标为"+midIndex);
            return ;
        }
    }

    binarySearch(arr,2,0,arr.length-1);

冒泡排序+二分查找

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