Question

我对堆算法的工作原理有一个很好的了解，但是我无法弄清楚如何将每个唯一的排列添加到数组中并根据算法的递归性质将其返回。

为什么只添加相同的排列，但控制台日志会打印出不同的排列？

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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堆的算法-JavaScript

1 个答案: