93. 复原 IP 地址(LeetCode)(dfs)

93. 复原 IP 地址

class Solution {
public:

    vector<string> res;

    vector<string> restoreIpAddresses(string s) {
        
        dfs(s, 0, 0, "");
        return res;    
    }
    //u第几位开始搜,k已经搜索了几个数
    void dfs(string &s, int u, int k, string path){
        if(u == s.size()){
            //将.去掉
            path.pop_back();
            if(k == 4) res.push_back(path);
            return;
        }
        if(k == 4) return;
        for(int i = u, t = 0; i < s.size(); ++i){
            if(i > u && s[u] == '0') break;
            t = t * 10 + s[i]-'0';
            if(t <= 255) dfs(s, i + 1, k + 1, path + to_string(t) + '.');
            else break;
        }
    }

};