add leetcode 516.cpp

Author: BWbwchen

leetcode/516.cpp

@@ -0,0 +1,22 @@
+class Solution {
+public:
+    int longestPalindromeSubseq(string s) {
+        int dp[1001][1001] = {0};
+        // dp[i][j] = the lps of s[i..j]
+        
+        for (int i = 0; i <= s.size(); ++i) {
+            dp[i][i] = 1;
+        }
+        
+        for (int j = 2; j <= s.size(); ++j) {
+            for (int i = j-1; i > 0; --i) {
+                if (s[i-1] == s[j-1]) {
+                    dp[i][j] = dp[i+1][j-1] + 2;
+                } else {
+                    dp[i][j] = max(dp[i+1][j], dp[i][j-1]);
+                }
+            }
+        }
+        return dp[1][s.size()];
+    }
+};