Leetcode 47. Permutations II

文章作者：Tyan
博客：noahsnail.com  |  CSDN  |  简书

1. Description

2. Solution

• Version 1

class Solution {
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>> result;
        build(result, nums, 0);
        return result;
    }
    
private:
    void build(vector<vector<int>>& result, vector<int>& nums, int start) {
        if(start == nums.size()) {
            result.push_back(nums);
            return;
        }
        unordered_map<int, int> duplicate;
        for(int i = start; i < nums.size(); i++) {
            if(duplicate.count(nums[i]) > 0) {
                continue;
            }
            else {
                duplicate[nums[i]]++;
            }
            swap(nums[start], nums[i]);
            build(result, nums, start + 1);
            swap(nums[start], nums[i]);
        }
    }
        
    void swap(int& a, int& b) {
        int temp = a;
        a = b;
        b = temp;
    }
};

• Version 2

class Solution {
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        vector<vector<int>> result;
        build(result, nums, 0);
        return result;
    }
    
private:
    void build(vector<vector<int>>& result, vector<int>& nums, int start) {
        if(start == nums.size()) {
            result.push_back(nums);
            return;
        }
        unordered_set<int> duplicate;
        for(int i = start; i < nums.size(); i++) {
            int size = duplicate.size();
            duplicate.insert(nums[i]);
            if(size == duplicate.size()) {
                continue;
            }
            swap(nums[start], nums[i]);
            build(result, nums, start + 1);
            swap(nums[start], nums[i]);
        }
    }
        
    void swap(int& a, int& b) {
        int temp = a;
        a = b;
        b = temp;
    }
};

Reference

1. https://leetcode.com/problems/permutations-ii/description/