Create code2.cpp

005.longest_palindromic_substring/code2.cpp

@@ -0,0 +1,36 @@
+class Solution {
+public:
+    string longestPalindrome(string s) {
+        string exS = preProcess(s);
+        int n = exS.length();
+        vector<int> dp(n, 0);
+        int C = 0, R = 0;
+        for (int i = 1; i < n; i++) {
+            int j = 2 * C - i;
+            dp[i] = R > i ? min(R - i, dp[j]) : 0;
+            while (i - 1 - dp[i] >= 0 && i + 1 + dp[i] < n && exS[i - 1 - dp[i]] == exS[i + 1 + dp[i]]) dp[i]++;
+            if (R < i + dp[i]) {
+                R = i + dp[i];
+                C = i;
+            }
+        }
+        int len = 0, index = -1;
+        for (int i = 0; i < n; i++) {
+            if (dp[i] > len) {
+                len = dp[i];
+                index = i;
+            }
+        }
+        return s.substr((index - dp[index]) / 2, dp[index]);
+    }
+
+    string preProcess(string s) {
+        string ans;
+        ans.push_back('#');
+        for (int i = 0; i < s.length(); i++) {
+            ans.push_back(s[i]);
+            ans.push_back('#');
+        }
+        return ans;
+    }
+};