题目描述
Evaluate the value of an arithmetic expression in Reverse Polish Notation.
Valid operators are+,-,*,/. Each operand may be an integer or another expression.
Some examples:
["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6
/**
* @author gentleKay
* Given a binary tree, find its minimum depth. 给定二叉树，求其最小深度。
* The minimum depth is the number of nodes along the shortest path from the root node down to the nearest leaf node.
* 最小深度是从根节点到最近的叶节点沿最短路径的节点数。
*/
public class Main01 {
public static void main(String[] args) {
// TODO Auto-generated method stub
TreeNode root = new TreeNode(4);
root.left = new TreeNode(2);
root.left.left = new TreeNode(1);
root.left.right = new TreeNode(3);
root.right = new TreeNode(6);
root.right.left = new TreeNode(5);
root.right.right = new TreeNode(7);
root.right.right.right = new TreeNode(8);
System.out.println(Main01.run(root));
}
public static class TreeNode {
int val;
TreeNode left;
TreeNode right;
TreeNode(int x) { val = x; }
}
public static int run(TreeNode root) {
if (root == null) {
return 0;
}
if (root.left == null) {
return run(root.right) + 1;
}
if (root.right == null) {
return run(root.left) + 1;
}
return Math.min(run(root.left)+1, run(root.right)+1);
}
}
Stack 方法：
