如果我使用两个“if”语句而不是仅使用“if / else”语句，为什么二进制搜索算法不起作用？ [关闭]

Question

此代码块完美运行。这是一个用javascript编写的二进制搜索算法。我是从网站上收集的。

function binarySearch(arr, target) {
    let left = 0;
    let right = arr.length - 1;
    while (left <= right) {
        const mid = left + Math.floor((right - left) / 2);
        if (arr[mid] === target) {
            return mid;
        }
        if (arr[mid] < target) {
            left = mid + 1;
        } else {
            right = mid - 1;
        }
    }
    return -1;
}

var result = binarySearch([2,3,4,5,6,7,8,9,10],2);
console.log(result);

但是，如果我以这种方式更改while循环中的代码它不起作用。我已经尝试了几次但无济于事。请帮我。问题是什么？

function binarySearch(arr, target) {
    let left = 0;
    let right = arr.length - 1;
    while (left <= right) {
        const mid = left + Math.floor((right - left) / 2);
        if (arr[mid] === target) {
            return mid;
        }

        if (arr[mid] < target) {
            left = mid + 1;
        }
        // Look here. Here is my problem
        if(arr[mid] > target){
            right = mid - 1;
        }
    }
    return -1;
}

var result = binarySearch([2,3,4,5,6,7,8,9,10],2);
console.log(result);

Answer 1

if (arr[mid] === target) {
    return mid;
}

if (arr[mid] < target) {
    left = mid + 1;
}

if(arr[mid] > target){
    right = mid - 1;
}

和

if (arr[mid] === target) {
    return mid;
}

if (arr[mid] < target) {
    left = mid + 1;
} else {
    right = mid - 1;
}

在这种情况下是等效的。