在javascript中反转数组？

Question

我在一本 javascript 书中解决这个问题以反转数组，我只是不知道为什么这段代码不起作用。有人可以解释一下吗？这段代码应该交换值，但它对数组没有任何作用。

let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];

function reverseArrayInPlace(array) {

    for (let start = 0, end = array.length - 1; start < array.length, end >= 0; start++, end--) {

        let x = array[start];

        array[start] = array[end];

        array[end] = x;

    }

    return array;

}

reverseArrayInPlace(nums);

console.log(nums);

Answer 1

您只需要检查startis 是否小于 then end。另一个检查是多余的，因为在end达到零之前，循环停止。function reverseArrayInPlace(array) {&nbsp; &nbsp; for (let start = 0, end = array.length - 1; start < end; start++, end--) {&nbsp; &nbsp; &nbsp; &nbsp; let x = array[start];&nbsp; &nbsp; &nbsp; &nbsp; array[start] = array[end];&nbsp; &nbsp; &nbsp; &nbsp; array[end] = x;&nbsp; &nbsp; }&nbsp; &nbsp; return array;}let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];reverseArrayInPlace(nums);console.log(nums);

Answer 2

此代码将每对元素交换两次：一次 whenstart < end和一次 when start > end。在您的 if 语句中，您想将中断条件更改为start < endand not start < array.length。let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];function reverseArrayInPlace(array) {&nbsp; &nbsp; for (let start = 0, end = array.length - 1; start < end; start++, end--) {&nbsp; &nbsp; &nbsp; &nbsp; let x = array[start];&nbsp; &nbsp; &nbsp; &nbsp; array[start] = array[end];&nbsp; &nbsp; &nbsp; &nbsp; array[end] = x;&nbsp; &nbsp; }&nbsp; &nbsp; return array;}reverseArrayInPlace(nums);console.log(nums);

Answer 3

只要数组中的值是整数，就可以执行按位异或 (XOR) 而无需临时变量。你也可以用一个控制变量来做到这一点，即i。时间复杂度为 O(n/2)。let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];function reverseIntArrayInPlace(arr) {&nbsp; for (let i = 0; i < Math.floor(arr.length / 2); i++) {&nbsp; &nbsp; arr[i] = arr[i] ^ arr[arr.length - 1 - i];&nbsp; &nbsp; arr[arr.length - 1 - i] = arr[i] ^ arr[arr.length - 1 - i];&nbsp; &nbsp; arr[i] = arr[i] ^ arr[arr.length - 1 - i];&nbsp; }&nbsp; return arr;}console.log(reverseIntArrayInPlace(nums));.as-console-wrapper { top: 0; max-height: 100% !important; }如果你想交换其他类型，那么你将需要一个临时变量。let nums = [1, 2, 3, 4, 5, 6, 7, 8, 9];function reverseArrayInPlace(arr) {&nbsp; for (let i = 0; i < Math.floor(arr.length / 2); i++) {&nbsp; &nbsp; const tmp = arr[i];&nbsp; &nbsp; arr[i] = arr[arr.length - 1 - i];&nbsp; &nbsp; arr[arr.length - 1 - i] = tmp;&nbsp; }&nbsp; return arr;}console.log(reverseArrayInPlace(nums));.as-console-wrapper { top: 0; max-height: 100% !important; }