491、递增子序列

讲解：https://programmercarl.com/0491.%E9%80%92%E5%A2%9E%E5%AD%90%E5%BA%8F%E5%88%97.html

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() && nums[i] < path.back()) || 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

讲解：https://programmercarl.com/0046.%E5%85%A8%E6%8E%92%E5%88%97.html

class Solution {
public:vector<vector<int>> result;vector<int> path;void backtracking (vector<int>& nums, vector<bool>& used) {// 此时说明找到了一组if (path.size() == nums.size()) {result.push_back(path);return;}for (int i = 0; i < nums.size(); i++) {if (used[i] == true) continue; // path里已经收录的元素，直接跳过used[i] = true;path.push_back(nums[i]);backtracking(nums, used);path.pop_back();used[i] = false;}}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

讲解：https://programmercarl.com/0047.%E5%85%A8%E6%8E%92%E5%88%97II.html

class Solution {
private:vector<vector<int>> result;vector<int> path;void backtracking (vector<int>& nums, vector<bool>& used) {// 此时说明找到了一组if (path.size() == nums.size()) {result.push_back(path);return;}for (int i = 0; i < nums.size(); i++) {// used[i - 1] == true，说明同一树枝nums[i - 1]使用过// used[i - 1] == false，说明同一树层nums[i - 1]使用过// 如果同一树层nums[i - 1]使用过则直接跳过if (i > 0 && nums[i] == nums[i - 1] && used[i - 1] == false) {continue;}if (used[i] == false) {used[i] = true;path.push_back(nums[i]);backtracking(nums, used);path.pop_back();used[i] = false;}}}
public:vector<vector<int>> permuteUnique(vector<int>& nums) {result.clear();path.clear();sort(nums.begin(), nums.end()); // 排序vector<bool> used(nums.size(), false);backtracking(nums, used);return result;}
};