代码随想录29

491. 递增子序列

class Solution {
    
private:
                vector<vector<int>> result;
                vector<int> path;        
                void backtracking(vector<int>& nums,int startIndex) {
                    if (path.size() > 1) {
                        result.push_back(path);
                    }
                    unordered_set<int> uset;
                    for (int i = startIndex; i < nums.size(); i++) {
                        if (!path.empty() && path.back() > nums[i] || uset.find(nums[i]) != uset.end()) {
                            continue;
                        }
                        uset.insert(nums[i]);
                        path.push_back(nums[i]);
                        backtracking(nums, i + 1);
                        path.pop_back();
                    }
                }
public:
    vector<vector<int>> findSubsequences(vector<int>& nums) {
                                result.clear();
                                path.clear();
                                backtracking(nums, 0);
                                return result;
    }
};

 

46. 全排列

class Solution {
private:
    vector<vector<int>> result;
    vector<int> path;
    void backtracking(vector<int>& nums, vector<bool>& used) {
        if (path.size() == nums.size()) {
            result.push_back(path);
            return;
        }
        for (int i = 0; i < nums.size(); i++) {
            if (used[i] == true) continue;
            used[i] = true;
            path.push_back(nums[i]);
            backtracking(nums,used);
            used[i] = false;
            path.pop_back();
        }
    }
public:
    vector<vector<int>> permute(vector<int>& nums) {
        result.clear();
        path.clear();
        vector<bool> used(nums.size(), false);
        backtracking(nums, used);
        return result;
    }
};

47. 全排列 II

class Solution {
private:
    vector<vector<int>> result;
    vector<int> path;
    void backtracking(vector<int>& nums, vector<bool> used) {
        if (path.size() == nums.size()) {
            result.push_back(path);
            return;
        }
        for (int i = 0; i < nums.size(); i++) {
            // if (used[i - 1] == true) 说明同一树枝nums[i - 1]使用过
            // if (used[i - 1] == false) 说明同一树层nums[i - 1]使用过
            if (i > 0 && used[i - 1] == false && nums[i] == nums[i - 1]) continue;
            if (used[i] == false) {
                path.push_back(nums[i]);
                used[i] = true;
                backtracking(nums, used);
                used[i] = false;
                path.pop_back();
            }
        }
    }
public:
    vector<vector<int>> permuteUnique(vector<int>& nums) {
        result.clear();
        path.clear();
        sort(nums.begin(), nums.end());
        vector<bool> used(nums.size(), false);
        backtracking(nums, used);
        return result;
    }
};