堆算法 - JavaScript

Question

我对堆算法的工作原理有很好的理解，但我无法弄清楚如何将每个唯一排列添加到数组中，并且 return 它基于算法的递归性质。

为什么只添加相同的排列但控制台日志打印出不同的排列？

var swap = function (array, pos1, pos2) {
  var temp = array[pos1];
  array[pos1] = array[pos2];
  array[pos2] = temp;
};

var heapsPermute = function (array, n, results = []) {
  n = n || array.length;
  if (n === 1) {
    results.push(array);
    console.log(array);
  } else {
    for (var i = 1; i <= n; i += 1) {
      heapsPermute(array, n - 1, results);
      if (n % 2) {
        var j = 1;
      } else {
        var j = i;
      }
      swap(array, j - 1, n - 1);
    }
  }

  return results;
};

console.log(heapsPermute(['a', 'b', 'c', 'd']));

Answer 1

您需要添加数组的副本，而不是数组及其对象引用。

results.push(array.slice());
//                ^^^^^^^^

var swap = function (array, pos1, pos2) {
  var temp = array[pos1];
  array[pos1] = array[pos2];
  array[pos2] = temp;
};

var heapsPermute = function (array, n, results = []) {
  n = n || array.length;
  if (n === 1) {
    results.push(array.slice());
  } else {
    for (var i = 1; i <= n; i += 1) {
      heapsPermute(array, n - 1, results);
      if (n % 2) {
        var j = 1;
      } else {
        var j = i;
      }
      swap(array, j - 1, n - 1);
    }
  }
  return results;
};

console.log(heapsPermute(['a', 'b', 'c', 'd']).map(a => a.join(' ')));

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