problems(rs): add “516. Longest Palindromic Subsequence”

Signed-off-by: Matej Focko <mfocko@redhat.com>

problems/longest-palindromic-subsequence.rs

@@ -0,0 +1,45 @@
+use std::cmp;
+
+struct Solution {}
+impl Solution {
+    pub fn longest_palindrome_subseq(s: String) -> i32 {
+        let mut longest: Vec<Vec<i32>> = vec![];
+        longest.resize_with(s.len(), || {
+            let mut nested: Vec<i32> = vec![];
+            nested.resize(s.len(), 0);
+
+            nested
+        });
+
+        for i in (0..s.len()).rev() {
+            longest[i][i] = 1;
+
+            for j in i + 1..s.len() {
+                if s.as_bytes()[i] == s.as_bytes()[j] {
+                    longest[i][j] = 2 + longest[i + 1][j - 1];
+                } else {
+                    longest[i][j] = cmp::max(longest[i + 1][j], longest[i][j - 1]);
+                }
+            }
+        }
+
+        longest[0][s.len() - 1]
+    }
+}
+
+fn main() {}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn with_skip() {
+        assert_eq!(Solution::longest_palindrome_subseq("bbbab".to_owned()), 4);
+    }
+
+    #[test]
+    fn without_skip() {
+        assert_eq!(Solution::longest_palindrome_subseq("cbbd".to_owned()), 2);
+    }
+}