谜题

穷举一个数组中各个元素的排列

策略

减而治之、递归

JavaScript解

复制代码 代码如下:
/**
* 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);

结果

复制代码 代码如下:
[ [ 'a', 'b', 'c' ],
[ 'a', 'c', 'b' ],
[ 'b', 'a', 'c' ],
[ 'b', 'c', 'a' ],
[ 'c', 'a', 'b' ],
[ 'c', 'b', 'a' ] ]