503. Next Greater Element II

monotonic stack

510. Inorder Successor in BST II

if curr has right child

---

if curr is left child, if curr is right child

516. Longest Palindromic Subsequence

dp

if (str[i] == str[j]) {
    dp[i][j] = 2 + dp[i + 1][j - 1]
} else {
    dp[i][j] = Math.max(dp[i + 1][j], dp[i][j - 1])
}

545. Boundary of Binary Tree

dfs

vector<int> left_boundaries; // push_back
vector<int> leaves; // push_back
deque<int> right_bondaries; // push_front

ret = [root, ...left_boundaries, ...leaves, ...right_bondaries]

556. Next Greater Element III

the same with next_permutation

583. Delete Operation for Two Strings

dp

---

xs.length + ys.length - 2 * longest_common_subsequence