LeetCode: Restore IP Addresses

erase的时候没考虑到.加上去之后删除位置的变化，基本一次过，少数次过

 1 class Solution {

 2 public:

 3     void dfs(vector<string> &ret, string tmp, string s, int dep, int maxsize, int beg) {

 4         if (beg > maxsize) return;

 5         if (dep == 4) {

 6             if (beg == maxsize) {

 7                 tmp.erase(beg+3, 1);

 8                 ret.push_back(tmp);

 9             }

10             return;

11         }

12         dfs(ret, tmp+s[beg]+'.',s, dep+1, maxsize, beg+1);

13         if (s.substr(beg, 2) >= "10" && s.substr(beg, 2) <= "99")

14             dfs(ret, tmp+s.substr(beg, 2)+'.', s, dep+1, maxsize, beg+2);

15         if (s.substr(beg, 3) >= "100" && s.substr(beg, 3) <= "255")

16             dfs(ret, tmp+s.substr(beg, 3)+'.', s, dep+1, maxsize, beg+3);

17     }

18     vector<string> restoreIpAddresses(string s) {

19         // Start typing your C/C++ solution below

20         // DO NOT write int main() function

21         vector<string> ret;

22         string tmp = "";

23         dfs(ret, tmp, s, 0, s.size(), 0);

24         return ret;

25     }

26 };

 C#

 1 public class Solution {

 2     public List<string> RestoreIpAddresses(string s) {

 3         List<string> ans = new List<string>();

 4         string tmp = "";

 5         dfs(ref ans, tmp, s, 0, s.Length, 0);

 6         return ans;

 7     }

 8     public void dfs(ref List<string> ans, string tmp, string s, int dep, int maxSize, int beg) {

 9         if (beg > maxSize) return;

10         if (dep == 4) {

11             if (beg == maxSize) {

12                 ans.Add(tmp.Substring(0, tmp.Length-1));

13             }

14             return;

15         }

16         if (beg < maxSize) dfs(ref ans, tmp + s[beg] + '.', s, dep + 1, maxSize, beg + 1);

17         if (beg + 2 <= maxSize && string.Compare(s.Substring(beg, 2), "10") >= 0 && string.Compare(s.Substring(beg, 2), "99") <= 0) 

18             dfs(ref ans, tmp + s.Substring(beg, 2) + '.', s, dep + 1, maxSize, beg + 2);

19         if (beg + 3 <= maxSize && string.Compare(s.Substring(beg, 3), "100") >= 0 && string.Compare(s.Substring(beg, 3), "255") <= 0)

20             dfs(ref ans, tmp + s.Substring(beg, 3) + '.', s, dep + 1, maxSize, beg + 3);

21     }

22 }

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