/**

* res.js

* @authors Joe Jiang ([email protected])

* @date 2017-04-03 21:52:31

*

* Problem: Given a collection of distinct numbers, return all possible permutations.

*

* @param {number[]} nums

* @return {number[][]}

*/

let permute = function(nums) {

let numlen = nums.length,

res = [];

if (numlen === 0) {

return res;

} else if (numlen === 1) {

res.push(nums);

return res;

}

return subpermute([], nums);

};

let subpermute = function(base, nums) {

let numlen = nums.length,

res = [];

if (numlen === 1) {

return [base.concat(nums)];

}

for (let i = 0; i < numlen; i++) {

let subarray = [];

for (let j = 0; j < numlen; j++) {

if (i === j) {

continue;

}

subarray.push(nums[j]);

}

let newbase = base.concat([nums[i]]);

res = res.concat(subpermute(newbase, subarray));

}

return res;

};

/**

* @param {number[]} nums

* @return {number[][]}

*/

var permute = function(nums) {

const len = nums.length;

if (!len) return [];

const res = [];

const enmurate = (preArr, candidates) => {

if (candidates.length === 1) return res.push([...preArr, ...candidates]);

for (let i = 0; i < candidates.length; i++) {

const temp = candidates.slice();

temp.splice(i, 1);

enmurate([...preArr, candidates[i]], temp);

}

}

enmurate([], nums.slice());

return res;

};