最大深度 = max(左子树深度, 右子树深度) + 1
Java#
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| class Solution {
public int maxDepth(TreeNode root) {
if (root == null) {
return 0;
}
return Math.max(maxDepth(root.left), maxDepth(root.right)) + 1;
}
}
|
迭代解法：
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| class Solution {
private static class State {
TreeNode node;
int depth;
State(TreeNode node, int depth) {
this.node = node;
this.depth = depth;
}
}
public int maxDepth(TreeNode root) {
if (root == null) {
return 0;
}
Deque<State> st = new ArrayDeque<>();
st.push(new State(root, 1));
int ans = 0;
while (!st.isEmpty()) {
State s = st.pop();
TreeNode node = s.node;
int d = s.depth;
ans = Math.max(ans, d);
if (node.left != null) {
st.push(new State(node.left, d + 1));
}
if (node.right != null) {
st.push(new State(node.right, d + 1));
}
}
return ans;
}
}
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BSF 解法
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| class Solution {
public int maxDepth(TreeNode root) {
if (root == null) {
return 0;
}
Deque<TreeNode> q = new ArrayDeque<>();
q.offer(root);
int depth = 0;
while (!q.isEmpty()) {
int size = q.size();
depth ++;
for (int i = 0; i < size; i ++) {
TreeNode node = q.poll();
if (node.left != null) {
q.offer(node.left);
}
if (node.right != null) {
q.offer(node.right);
}
}
}
return depth;
}
}
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