JavaScript實現窮舉排列(permutation)演算法謎題解答_javascript技巧

謎題

窮舉一個數組中各個元素的排列

策略

減而治之、遞迴

JavaScript解

複製代碼 代碼如下:

/**
 * Created by cshao on 12/23/14.
 */

function getPermutation(arr) {
  if (arr.length == 1) {
    return [arr];
  }

  var permutation = [];
  for (var i=0; i<arr.length; i++) {
    var firstEle = arr[i];
    var arrClone = arr.slice(0);
    arrClone.splice(i, 1);
    var childPermutation = getPermutation(arrClone);
    for (var j=0; j<childPermutation.length; j++) {
      childPermutation[j].unshift(firstEle);
    }
    permutation = permutation.concat(childPermutation);
  }
  return permutation;
}

var permutation = getPermutation(['a','b','c']);
console.dir(permutation);

結果

複製代碼 代碼如下:

[ [ 'a', 'b', 'c' ],
  [ 'a', 'c', 'b' ],
  [ 'b', 'a', 'c' ],
  [ 'b', 'c', 'a' ],
  [ 'c', 'a', 'b' ],
  [ 'c', 'b', 'a' ] ]