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MinDepth.java
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69 lines (63 loc) · 1.64 KB
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package ds;
/**
* 给定一个二叉树，找出其最小深度。
* <p>
* 最小深度是从根节点到最近叶子节点的最短路径上的节点数量。
* <p>
* 说明: 叶子节点是指没有子节点的节点。
* <p>
* 示例:
* <p>
* 给定二叉树 [3,9,20,null,null,15,7],
* <p>
* 3
* / \
* 9 20
* / \
* 15 7
* 返回它的最小深度 2.
*
* @author yangyi 2019年01月28日23:24:57
*/
public class MinDepth {
public class TreeNode {
int val;
TreeNode left;
TreeNode right;
}
public int minDepth(TreeNode root) {
if (root == null) {
return 0;
}
if (root.left == null) {
return minDepth(root.right) + 1;
}
if (root.right == null) {
return minDepth(root.left) + 1;
}
return Math.min(minDepth(root.left), minDepth(root.right)) + 1;
}
public TreeNode createTree() {
TreeNode node_3 = new TreeNode();
node_3.val = 3;
TreeNode node_9 = new TreeNode();
node_9.val = 9;
TreeNode node_20 = new TreeNode();
node_20.val = 20;
TreeNode node_15 = new TreeNode();
node_15.val = 15;
TreeNode node_7 = new TreeNode();
node_7.val = 7;
node_3.left = node_9;
node_3.right = node_20;
node_20.left = node_15;
node_20.right = node_7;
return node_3;
}
public static void main(String[] args) {
MinDepth minDepth = new MinDepth();
TreeNode node = minDepth.createTree();
int min = minDepth.minDepth(node);
System.out.println("最小深度为:" + min);
}
}