Question

我目前正在为我的扩展论文进行调查。我正在测试合并算法和快速排序算法之间的比较。我的结果出现这个怪异的异常。我的第二个for循环中的每个第一个排序返回的时间都比其余时间长得多。我不知道为什么，有人可以解释吗？

由于某种原因，JSFiddle将不会输出任何内容，尽管在本地运行时它可以正常工作。所以，我将代码发布在这里：

function generateRandomArray(l, min, max) {
  var a = [];

  for (var i = 0; i < l; i++) {
    a.push(Math.ceil(Math.random() * max + min - 1));
  }

  return a;
}

function quickSort(a) {
  var less = [],
    pivotList = [],
    greater = [];

  if (a.length <= 1) return a;

  var pivot = a[0];

  for (var i = 0; i < a.length; i++) {
    if (a[i] < pivot) less.push(a[i]);
    else if (a[i] > pivot) greater.push(a[i]);
    else pivotList.push(a[i]);
  }

  less = quickSort(less);
  greater = quickSort(greater);

  return less.concat(pivotList, greater);
}

function mergeSort(left, right) {
  if (!left) return right;
  if (!right) return left;

  var result = [],
    leftIndex = 0,
    rightIndex = 0;

  while (leftIndex < left.length & rightIndex < right.length) {
    if (left[leftIndex] <= right[rightIndex]) {
      result.push(left[leftIndex]);
      leftIndex++;
    } else {
      result.push(right[rightIndex]);
      rightIndex++;
    }
  }

  if (leftIndex != left.length) {
    var temp = left.slice(leftIndex, left.length);

    result = result.concat(temp);
  } else if (rightIndex != right.length) {
    var temp = right.slice(rightIndex, right.length);

    result = result.concat(temp);
  }

  return result;
}

function mergeSortSplit(a) {
  if (a.length <= 1) return a;

  var middle = Math.floor(a.length / 2);

  var left = a.slice(0, middle),
    right = a.slice(middle, a.length);

  left = mergeSortSplit(left);
  right = mergeSortSplit(right);

  return mergeSort(left, right);
}

window.onload = function() {
  var timeResults = [
    [[], [], [], [], []],
    [[], [], [], [], []]
  ];

  for (var i = 0; i < 10; i++) {
    for (var j = 3; j < 6; j++) {
      var array = generateRandomArray(Math.pow(10, j), 1, 100);

      var mergeSortTime = window.performance.now();
      mergeSortSplit(array);
      timeResults[0][j - 3].push(window.performance.now() - mergeSortTime);

      var quickSortTime = window.performance.now();
      quickSort(array);
      timeResults[1][j - 3].push(window.performance.now() - quickSortTime);
    }
  }

  for (var i = 0; i < timeResults.length; i++) {
    document.getElementById("demo").innerHTML += "<b>" + (i + 1) + ". </b><br>";

    for (var j = 0; j < timeResults[i].length; j++) {
      document.getElementById("demo").innerHTML += "<b>" + Math.pow(10, j + 3) + ": </b>";

      for (k = 0; k < timeResults[i][j].length; k++) {
        document.getElementById("demo").innerHTML += timeResults[i][j][k] + "<b> | </b>";
      }

      document.getElementById("demo").innerHTML += "<br><br>";
    }

    document.getElementById("demo").innerHTML += "<br><br><br>";
  }

  console.log(timeResults);
}

<html>

<head>
  <meta charset="utf-8">
  <title>EE Investigation</title>
  <script type="text/javascript" src="index.js"></script>
</head>

<body>
  <p id="demo"></p>
</body>

</html>

合并和快速排序时间导致异常

0 个答案: