39. 组合总和 - 力扣（LeetCode）

class Solution {private:vector<int> path;vector<vector<int>> result;
public:void trackbacking(vector<int>& candidates,int target,int sum,int startIndex){if(sum>target)return;if(sum==target){result.push_back(path);return;}for(int i=startIndex;i<candidates.size();i++){sum+=candidates[i];path.push_back(candidates[i]);trackbacking(candidates,target,sum,i);sum-=candidates[i];path.pop_back();}}vector<vector<int>> combinationSum(vector<int>& candidates, int target) {trackbacking(candidates,target,0,0);return result;}
};

 40. 组合总和 II - 力扣（LeetCode）

回溯算法中的去重，树层去重树枝去重，你弄清楚了没？| LeetCode:40.组合总和II_哔哩哔哩_bilibili

class Solution {
private:vector<vector<int>> result;vector<int> path;void backtracking(vector<int>& candidates, int target, int sum, int startIndex, vector<bool>& used) {if (sum == target) {result.push_back(path);return;}for (int i = startIndex; i < candidates.size() && sum + candidates[i] <= target; i++) {if (i > 0 && candidates[i] == candidates[i - 1] && used[i - 1] == false) {continue;}sum += candidates[i];path.push_back(candidates[i]);used[i] = true;backtracking(candidates, target, sum, i + 1, used);used[i] = false;sum -= candidates[i];path.pop_back();}}public:vector<vector<int>> combinationSum2(vector<int>& candidates, int target) {vector<bool> used(candidates.size(), false);path.clear();result.clear();sort(candidates.begin(), candidates.end());backtracking(candidates, target, 0, 0, used);return result;}
};

 131. 分割回文串 - 力扣（LeetCode）

带你学透回溯算法-分割回文串（对应力扣题目：131.分割回文串）| 回溯法精讲！_哔哩哔哩_bilibili

class Solution {
private:vector<vector<string>> result;vector<string> path;void backtracking(const string&s,int startindex){if(startindex>=s.size()){result.push_back(path);return ;}for(int i=startindex;i<s.size();i++){if(isPalindrome(s,startindex,i)){string str=s.substr(startindex,i-startindex+1);path.push_back(str);}elsecontinue;backtracking(s,i+1);path.pop_back();}}bool isPalindrome(const string&s ,int start,int end){for(int i=start,j=end;i<j;i++,j--){if(s[i]!=s[j])return false;}return true;}
public:vector<vector<string>> partition(string s) {backtracking(s,0);return result;}
};