代码随想录day26||● 39. 组合总和● 40.组合总和II● 131.分割回文串

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);
            }
            else
            continue;
            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;
    }
};