03-树3 Tree Traversals Again-优快云博客

本文链接：https://blog.youkuaiyun.com/xvcain/article/details/108148731

本文详细介绍了一种使用Java实现的树的遍历算法，包括读取树结构、栈操作和后序遍历过程。通过解析输入数据，构建树节点，并运用栈来辅助遍历，最终实现了树的后序遍历输出。

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//03-树3 Tree Traversals Again
import java.util.Scanner;
import java.util.Stack;

class node{
	int number = 0;
	int left = 30;
	int right = 30;
}

public class Main {
	final static int Max_Size = 30;
	static int count = 0;

	static node[] Read(Scanner s) {
		Stack<Integer> stack = new Stack<Integer>();
		String prec, curc;
		int n = s.nextInt();
		node[] T = new node[Max_Size + 1];
		int x = 0;
		int f = 1;
		prec = s.next();
		int top = 0;
		x = s.nextInt();
		T[0] = new node();
		T[0].number = x;
		top ++;
		stack.push(0);
		if(n == 1) {
			curc = s.next();
		}
		for(int i = 0; i < 2 * n -2; i ++) {
			curc = s.next();
			if(curc.equals("Push")) {
				x = s.nextInt();
				if(prec.equals("Push")) {
					T[f] = new node();
					T[f - 1].left = f;
					T[f].number = x;
					stack.push(f);
					f ++;
					top ++;
				}
				else if(prec.equals("Pop")) {
					T[f] = new node();
					T[f].number = x;
					T[top].right = f;
					stack.push(f);
					f ++;
					top ++;
				}
				prec = "Push";
			}
			if(curc.equals("Pop")) {
				top = stack.pop();
				prec = "Pop";
			}
		}
		return T;
	}
	
	static void PostOrderTraversal(node N, node[] T) {
		int n = 0;
		while(T[n] != null) {
			n ++;
		}
		if (N != null)
	    {
	        PostOrderTraversal(T[N.left], T);
	        PostOrderTraversal(T[N.right], T);
	        System.out.print(N.number);
	        count ++;
	        if(count < n) {
	        	System.out.print(" ");
	        }
	    }
	}
	
	public static void main(String args[]) {
		Scanner s = new Scanner(System.in);
		node[] T = Read(s);
		s.close();
		//System.out.println();
		PostOrderTraversal(T[0], T);
	}
}