In this Leetcode Permutations problem solution we have given an array nums of distinct integers, return all the possible permutations. You can return the answer in any order.

Leetcode Permutations problem solution


Problem solution in Python.

def permute(self, nums):
    if not nums: 
       return [[]]
    return [[nums[i]] + j for i in xrange(len(nums)) for j in self.permute(nums[:i]+nums[i+1:])]



Problem solution in Java.

class Solution {
    public List<List<Integer>> permute(int[] nums) {
        List<List<Integer>> ans = new ArrayList<>();
        List<Integer> ds = new ArrayList<>();
        boolean[] freq = new boolean[nums.length];
        fun(nums, ds,ans, freq);
        return ans;
    }
    public void fun(int[] nums,List<Integer> ds,List<List<Integer>> ans,boolean[] freq){
        if(ds.size()==nums.length){
            ans.add(new ArrayList<>(ds));
            return ;
        }
        for(int i=0;i<nums.length;i++){
            if(!freq[i]){
                freq[i] = true;
                ds.add(nums[i]);
                fun(nums, ds,ans, freq);
                ds.remove(ds.size()-1);
                freq[i] = false;
            }
        }
    }
}


Problem solution in C++.

class Solution {
public:
    vector<vector<int>> result;
    
    void dfs(vector<int> &nums, int n){
        
        if(n==nums.size()) {
            result.push_back(nums);
            return;
        }
        else{
            for(int i=n;i<nums.size();i++){
                swap(nums[i],nums[n]);
                dfs(nums,n+1);
                swap(nums[i],nums[n]);
            }
        }
    }
    
    vector<vector<int>> permute(vector<int>& nums) {
        dfs(nums,0);
        return result;
    }
};


Problem solution in C.

void permute_step(int* p, int n, int* k,int** rp,int nn)
{
    int tmp;
    if (n == 1)
    {
        rp[*k][n - 1] = p[0];
        for (int i = 0;i < nn;i++)
        {   
            if (rp[*k][i] <= -1024) rp[*k][i] = rp[(*k) - 1][i];
        }
        (*k)++;
    }
    else
    {
        for (int i = 0;i < n;i++)
        {
            rp[*k][n - 1] = p[i];tmp = p[i];p[i] = p[0];
            permute_step(p + 1, n - 1, k, rp, nn);
            p[0] = p[i];p[i] = tmp;
        }
    }
}

int** permute(int* nums, int numsSize, int* returnSize) {
    *returnSize = 1;
    for (int i = 1;i <= numsSize;i++)
        *returnSize *= i;
    int** r = (int**)malloc(sizeof(int*)*(*returnSize));
    for (int i = 0;i < *returnSize;i++)
    {
        r[i] = (int*)malloc(sizeof(int)*numsSize);
        for (int j = 0;j < numsSize;j++)
            r[i][j] = -1024;
    }
    int k = 0;int* kp = &k;
    permute_step(nums, numsSize, kp, r, numsSize);
    return r;
}