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Javascript Array.sort实现?

保持可爱mmm 2020-01-16 16:06:05 80

JavaScript Array#sort()函数使用哪种算法?我知道可以使用各种形式的参数和函数来执行不同种类的排序,我只是对香草排序使用哪种算法感兴趣。

算法 JavaScript 前端开发
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  • 保持可爱mmm
    2020-01-16 16:06:33

    JS不需要使用特定的排序算法的草稿要求。正如许多人在这里提到的那样,Mozilla使用合并排序,但是在Chrome的v8源代码中,直到今天,对于较小的数组,它都使用QuickSort和InsertionSort。

    V8引擎来源

    从807-891行

    var QuickSort = function QuickSort(a, from, to) { var third_index = 0; while (true) { // Insertion sort is faster for short arrays. if (to - from <= 10) { InsertionSort(a, from, to); return; } if (to - from > 1000) { third_index = GetThirdIndex(a, from, to); } else { third_index = from + ((to - from) >> 1); } // Find a pivot as the median of first, last and middle element. var v0 = a[from]; var v1 = a[to - 1]; var v2 = a[third_index]; var c01 = comparefn(v0, v1); if (c01 > 0) { // v1 < v0, so swap them. var tmp = v0; v0 = v1; v1 = tmp; } // v0 <= v1. var c02 = comparefn(v0, v2); if (c02 >= 0) { // v2 <= v0 <= v1. var tmp = v0; v0 = v2; v2 = v1; v1 = tmp; } else { // v0 <= v1 && v0 < v2 var c12 = comparefn(v1, v2); if (c12 > 0) { // v0 <= v2 < v1 var tmp = v1; v1 = v2; v2 = tmp; } } // v0 <= v1 <= v2 a[from] = v0; a[to - 1] = v2; var pivot = v1; var low_end = from + 1; // Upper bound of elements lower than pivot. var high_start = to - 1; // Lower bound of elements greater than pivot. a[third_index] = a[low_end]; a[low_end] = pivot;

      // From low_end to i are elements equal to pivot.
      // From i to high_start are elements that haven't been compared yet.
      partition: for (var i = low_end + 1; i < high_start; i++) {
        var element = a[i];
        var order = comparefn(element, pivot);
        if (order < 0) {
          a[i] = a[low_end];
          a[low_end] = element;
          low_end++;
        } else if (order > 0) {
          do {
            high_start--;
            if (high_start == i) break partition;
            var top_elem = a[high_start];
            order = comparefn(top_elem, pivot);
          } while (order > 0);
          a[i] = a[high_start];
          a[high_start] = element;
          if (order < 0) {
            element = a[i];
            a[i] = a[low_end];
            a[low_end] = element;
            low_end++;
          }
        }
      }
      if (to - high_start < low_end - from) {
        QuickSort(a, high_start, to);
        to = low_end;
      } else {
        QuickSort(a, from, low_end);
        from = high_start;
      }
    }
    

    }; 问题来源于stack overflow

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