DailyPractice.2023.10.22

1.[39. 组合总和]

39. 组合总和

class Solution {
public:
vector<vector<int>> res;
vector<int> path;
	void dfs(vector<int>& candidates,int target,int start,int sum) {
		if (sum == target) {
			res.push_back(path);
			return ;
		}
		for (int i = start; i < candidates.size() && sum + candidates[i] <= target; i++) {
			path.push_back(candidates[i]);
			dfs(candidates,target,i,sum + candidates[i]);
			path.pop_back();
		}
	}
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
    	if (candidates.size() == 0) return res;
        sort(candidates.begin(),candidates.end());
        dfs(candidates,target,0,0);
       	return res;
    }
};

2.[22. 括号生成]

22. 括号生成

class Solution {
public:
vector<string> res;
string path;
	void process(int open,int close,int n) {
		if (path.size() == n * 2) {
			res.push_back(path);
			return ;
		}
		if (open < n) {
			path.push_back('(');
            process(open + 1,close,n);
            path.pop_back();
		}
		if (close < open) {
			path.push_back(')');
            process(open,close + 1,n);
            path.pop_back();
		}
	}
    vector<string> generateParenthesis(int n) {
		if (n == 0) return res;
		if (n == 1) return {"()"};
		process(0,0,n);
		return res;
    }
};

3.[79. 单词搜索]

class Solution {
public:
int m, n;
int dx[4] = {-1, 1, 0, 0};
int dy[4] = {0, 0, -1, 1};
vector<vector<bool>> visited;
    bool solveHelper(vector<vector<char>>& board, int x, int y, string& word, int idx)  {
        if (idx == word.size() - 1 && board[x][y] == word[idx]) {
            return true;
        }
        else if(board[x][y]!=word[idx]){
            return false;
        }
        visited[x][y] = true;
        for (int i = 0; i < 4; i++) {
             int nx=x+dx[i], ny=y+dy[i];
             if (nx >= 0 && nx < m && ny >= 0 && ny < n && !visited[nx][ny]){
                 if(solveHelper(board, nx, ny, word, idx+1)){
                    return true;
                }
             }
        }
        visited[x][y] = false;
        return false;
    }
    bool exist(vector<vector<char>>& board, string word) {
         m = board.size(), n=board[0].size();
        visited = vector<vector<bool>>(m, vector<bool>(n, false));
        for(int i=0; i<m; i++){
            for(int j=0; j<n; j++){
                if(solveHelper(board, i, j, word, 0)){
                    return true;
                }
            }
        }
        return false;
    }
};

4.[131. 分割回文串]

131. 分割回文串

class Solution {
public:
vector<vector<string>> res;
string path;
	void process(string &s,int index) {
		if (index >= s.size()) {
			res.push_back(path);
			return ;
		}
		for (int i = index; i < s.size(); i++) {
			if (isVaild(s,index,i) {
				string str = s.substr(index,i - index + 1);
				path.push_back(str);
			}
			else {
				continue;
			}
			 process(s,i + 1);
            path.pop_back();
		}
		
	}
	bool isVaild(string &s,int open,int close) {
		for (int i = open,j = close; i < j; i ++,j --） {
			if (s[i] != s[j]) {
				return false;
			}
		}
		return true;
	}
    vector<vector<string>> partition(string s) {
		if (s.size() == 1) return res;
		process(s,0);
		return res;
    }
};