题解 | #数字字符串转化成IP地址#

class Solution {
public:
    /**
     * 
     * @param s string字符串 
     * @return string字符串vector
     */
    vector<string> restoreIpAddresses(string s) {
        // write code here
        vector<string> ans;
        function<void(string, string, int, int)> dfs = [&](string ip, string cur, int point, int idx) {
            if (idx == s.length()) {
                if (point == 3) ans.push_back(ip);
                return;
            }
            for (int i = idx; i < s.length(); i++) {
                cur += s[i];
                if (stoi(cur) >= 256) return;
                if (cur.length() > 1 and cur[0] == '0') return;
                if (i + 1 == s.length()) {
                    dfs(ip + cur, "", point, i + 1);
                } else {
                    dfs(ip + cur + '.', "", point + 1, i + 1);
                }
            }
        };
        dfs("", "", 0, 0);
        return ans;
    }
};