Permutations

Given a collection of numbers, return all possible permutations.

For example,
[1,2,3] have the following permutations:
[1,2,3], [1,3,2], [2,1,3], [2,3,1], [3,1,2], and [3,2,1].

题意

列出数组中元素全排列

思路

这道题应该可以用next permutaion来解，这里我用的是DFS

public class Solution {
    private boolean isVisited[];
    
    public List<List<Integer>> permute(int[] num) {   
        isVisited = new boolean[num.length];
        List<List<Integer>> result = new ArrayList<List<Integer>>();
        dfs(result, num, 0, new ArrayList<Integer>());
        
        return result;
    }
    
    /**
     * 深度遍历数组
     * @param num
     * @param dep
     */
    private void dfs(List<List<Integer>> result, int num[], int dep, List<Integer> cur){
        if(dep != num.length){
            for(int i = 0; i < num.length; i++){
                if(isVisited[i] == false){
                    isVisited[i] = true;
                    cur.add(num[i]);
                    dfs(result, num, dep + 1, cur);
                    isVisited[i] = false;
                    cur.remove(cur.size() - 1);
                }//if
            }//for
        }//if
        else{
            result.add(new ArrayList<Integer>(cur));
        }
    }
}