MinimumDepthBinaryTree
MinimumDepthBinaryTree.java 源码
package algorithm.recursion;
import java.util.LinkedList;
import java.util.Queue;
/**
* @author roseduan
* @time 2020/9/24 7:48 下午
* @description 二叉树的最小深度
*/
public class MinimumDepthBinaryTree {
/**
* 递归，深度优先遍历的思想
*/
public int minDepth(TreeNode root) {
if (root == null) {
return 0;
}
if (root.left == null && root.right == null) {
return 1;
}
int res = Integer.MAX_VALUE;
if (root.left != null) {
res = Math.min(minDepth(root.left), res);
}
if (root.right != null) {
res = Math.min(minDepth(root.right), res);
}
return res + 1;
}
/**
* 广度优先遍历
*/
public int minDepth2(TreeNode root) {
if (root == null) {
return 0;
}
Queue<TreeNode> queue = new LinkedList<>();
queue.add(root);
int level = 0;
while (!queue.isEmpty()) {
int n = queue.size();
level++;
for (int i = 0; i < n; i++) {
TreeNode node = queue.poll();
if (node.left == null && node.right == null) {
return level;
}
if (node.left != null) {
queue.add(node.left);
}
if (node.right != null) {
queue.add(node.right);
}
}
}
return -1;
}
public static class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int val) { this.val = val; }
TreeNode(int val, TreeNode left, TreeNode right) {
this.val = val;
this.left = left;
this.right = right;
}
}
}
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