Question

我正在尝试在JS中进行合并排序，并且不知道我在哪里弄乱。我希望它返回[1,2,3,4]并返回[1,1,1,4]。

它需要改变哪些部分？

var array = [3,2,1,4]

function mergeSort(array) {
    if (array.length === 1) {
        return array
    } else {
        mid = Math.floor(array.length/2)
        left = mergeSort(array.slice(0, mid))
        right = mergeSort(array.slice(mid, array.length))
        return merge(left, right)
    }
}

function merge(left, right) {
    var leftIndex = 0
    var rightIndex = 0
    var sorted = []

    while (leftIndex < left.length && rightIndex < right.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            sorted.push(left[leftIndex])
            leftIndex += 1
        } else {
            sorted.push(right[rightIndex])
            rightIndex += 1
        }
    }

    if (leftIndex < left.length) {
        sorted = sorted.concat(left.slice(leftIndex))
    } else if (rightIndex < right.length) {
        sorted = sorted.concat(right.slice(rightIndex))
    }
    return sorted
}

console.log(mergeSort(array))

Answer 1

它工作正常（带有一些声明和分号）。

var array = [3, 2, 1, 4],
    result = mergeSort(array);

function mergeSort(array) {
    var mid, left, right;
    if (array.length === 1) {
        return array;
    } else {
        mid = Math.floor(array.length / 2);
        left = mergeSort(array.slice(0, mid));
        right = mergeSort(array.slice(mid, array.length));
        return merge(left, right);
    }
}

function merge(left, right) {
    var leftIndex = 0,
        rightIndex = 0,
        sorted = [];

    while (leftIndex < left.length && rightIndex < right.length) {
        if (left[leftIndex] <= right[rightIndex]) {
            sorted.push(left[leftIndex]);
            leftIndex += 1;
        } else {
            sorted.push(right[rightIndex]);
            rightIndex += 1;
        }
    }

    if (leftIndex < left.length) {
        sorted = sorted.concat(left.slice(leftIndex));
    } else if (rightIndex < right.length) {
        sorted = sorted.concat(right.slice(rightIndex));
    }
    return sorted;
}

document.write('<pre>' + JSON.stringify(result, 0, 4) + '</pre>');

Answer 2

你有一个范围问题。您尚未声明left，right和mid变量，因此它们被视为隐式全局变量并导致混乱。

修正：

function mergeSort(array) {
    if (array.length === 1) {
        return array
    } else {
        var mid = Math.floor(array.length/2)
        var left = mergeSort(array.slice(0, mid))
        var right = mergeSort(array.slice(mid, array.length))
        return merge(left, right)
    }
}

javascript中的merge sort返回重复的元素

2 个答案: