110. Balanced Binary Tree - LeetCode

Question

110. Balanced Binary Tree

Solution

題目大意：判斷一個二叉樹是否是平衡二叉樹

思路：定義個boolean來記錄每一個子節點是否平衡

Java實現：

public boolean isBalanced(TreeNode root) {
    boolean[] balanced = {true};
    height(root, balanced);
    return balanced[0];
}

private int height(TreeNode node, boolean[] balanced) {
    if (node == null) return 0;
    int leftHeight = height(node.left, balanced);
    int rightHeight = height(node.right, balanced);
    balanced[0] = balanced[0] && !(Math.abs(leftHeight - rightHeight) > 1);
    return balanced[0] ? Math.max(leftHeight, rightHeight) + 1 : -1;
}

Ref

https://www.youtube.com/watch?v=C75oWiy0bWM