前端算法之归并排序

 
function mergeSort(arr) { // 采用自上而下的递归方法
    var len = arr.length;
    if (len < 2) {
        return arr;
    }
    var middle = Math.floor(len / 2),
        left = arr.slice(0, middle),
        right = arr.slice(middle);
    return merge(mergeSort(left), mergeSort(right));
}
 
 
function merge(left, right) {
    var result = [];
 
 
    while (left.length>0 && right.length>0) {
        if (left[0] <= right[0]) {
            result.push(left.shift());
        }else {
            result.push(right.shift());
        }
    }
 
 
    while (left.length)
        result.push(left.shift());
 
 
    while (right.length)
        result.push(right.shift());
 
 
    return result;
}