solution for longest palindromic subsequence

Author: VIBEXD

longest-palindromic-subsequence.cpp

@@ -0,0 +1,35 @@
+class Solution
+{
+public:
+    int check(string &s, int L, int R)
+    {
+        while (L >= 0 and R < s.length() and s[L] == s[R])
+        {
+            L--;
+            R++;
+        }
+        return R - L - 1;
+    }
+
+    string longestPalindrome(string s)
+    {
+
+        int ans = 0, st = 0;
+        int n = s.length();
+
+        for (int i = 0; i < n; i++)
+        {
+            int len1 = check(s, i, i);
+            int len2 = check(s, i, i + 1);
+
+            int len = max(len1, len2);
+
+            if (len > ans)
+            {
+                ans = len;
+                st = i - (len - 1) / 2;
+            }
+        }
+        return s.substr(st, ans);
+    }
+};