LeetCode: Longest Palindromic Substring

自己的large没过，找到的网上答案跟一开始的想法是一样的，不过被网上的一个string的substr用法给坑了。。string.substr(strposstart, length)

 1 class Solution {
 2 public:
 3     string longestPalindrome(string s) {
 4         // Start typing your C/C++ solution below
 5         // DO NOT write int main() function
 6         if (s == "" || s.length() <= 1) return s;  
 7         string longestPalindrome = "";  
 8         for (int i = 0; i < s.length() - 1; i++) {  
 9             string palindrome = getLongestPalindrome(s, i, i);  
10             if (palindrome.length() > longestPalindrome.length()) {  
11                 longestPalindrome = palindrome;  
12             }  
13               
14             palindrome = getLongestPalindrome(s, i, i + 1);  
15             if (palindrome.length() > longestPalindrome.length()) {  
16                 longestPalindrome = palindrome;  
17             }   
18         }  
19         return longestPalindrome;  
20     }
21     string getLongestPalindrome(string s, int l, int r) {  
22         int length = s.length();  
23         while(l >= 0 && r < length && s[l] == s[r]) {  
24             l--;  
25             r++;  
26         }  
27         return s.substr(l + 1, r - l - 1);  
28     }  
29 };

下面这段代码更好

 1 class Solution {
 2 public:
 3     string longestPalindrome(string s) {
 4         // IMPORTANT: Please reset any member data you declared, as
 5         // the same Solution instance will be reused for each test case.
 6         string res;
 7         for (int i = 0; i < s.size(); i++) {
 8             int left, right;
 9             left = right = i;
10             while (left >= 0 && right < s.size() && s[left] == s[right]) {
11                 left--;
12                 right++;
13             }
14             if (right - 1 - (left + 1) + 1 > res.size()) res = s.substr(left+1, right-left-1);
15             left = i, right = i+1;
16             while (left >= 0 && right < s.size() && s[left] == s[right]) {
17                 left--;
18                 right++;
19             }
20             if (right - left - 1 > res.size()) res = s.substr(left+1, right-left-1);
21         }
22         return res;
23     }
24 };

 1 public class Solution {
 2     public string LongestPalindrome(string s) {
 3         string ans = "";
 4         for (int i = 0; i < s.Length; i++) {
 5             int left = i, right = i;
 6             while (left >= 0 && right < s.Length && s[left] == s[right]) {
 7                 left--;
 8                 right++;
 9             }
10             if (right - left - 1 > ans.Length) ans = s.Substring(left + 1, right - left - 1);
11             left = i; right = i + 1;
12             while (left >= 0 && right < s.Length && s[left] == s[right]) {
13                 left--;
14                 right++;
15             }
16             if (right - left - 1 > ans.Length) ans = s.Substring(left + 1, right - left  - 1);
17         }
18         return ans;
19     }
20 }

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posted @ 2013-04-04 03:00 ying_vincent 阅读(230) 评论(0) 收藏举报

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