PAT (Advanced Level) Practice 1102 Invert a Binary Tree (25分) (层序遍历)

1.题目

The following is from Max Howell @twitter:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can't invert a binary tree on a whiteboard so fuck off.

Now it's your turn to prove that YOU CAN invert a binary tree!

Input Specification:

Each input file contains one test case. For each case, the first line gives a positive integer N (≤10) which is the total number of nodes in the tree -- and hence the nodes are numbered from 0 to N−1. Then N lines follow, each corresponds to a node from 0 to N−1, and gives the indices of the left and right children of the node. If the child does not exist, a - will be put at the position. Any pair of children are separated by a space.

Output Specification:

For each test case, print in the first line the level-order, and then in the second line the in-order traversal sequences of the inverted tree. There must be exactly one space between any adjacent numbers, and no extra space at the end of the line.

Sample Input:

8
1 -
- -
0 -
2 7
- -
- -
5 -
4 6

Sample Output:

3 7 2 6 4 0 5 1
6 5 7 4 3 2 0 1

2.代码

#include<iostream>
#include<queue>
#include<string>
#include<cstring>
using namespace std;
struct node
{
	int data;
	int left;
	int right;
}list[13],temp;
int mark[13];
int head;
void levelorder()
{
	queue<node>out;
	bool space = false;
	out.push(list[head]);
	while (!out.empty())
	{
		 temp = out.front(); out.pop();
		printf("%s%d", space == false ? "" : " ",temp.data); space = true;
		if(temp.right!=-1)out.push(list[temp.right]);
		if (temp.left != -1)out.push(list[temp.left]);
	}

}
bool space = false;
void inorder(int head)
{
	if (head == -1)return;
	if(list[head].right!=-1)inorder(list[list[head].right].data);
	printf("%s%d", space == false ? "" : " ", list[head].data); space = true;
	if (list[head].left != -1)inorder(list[list[head].left].data);
}
int main()
{
	int n;
	scanf("%d", &n);
	string a, b;
	for (int i = 0; i < n; i++)
	{
		cin >> a >> b;
		 list[i].data=i;
		 if (a == "-")list[i].left =-1;
		 else { list[i].left = stoi(a); mark[stoi(a)] = 1; }
		 if (b == "-")list[i].right = -1;
		 else { list[i].right = stoi(b); mark[stoi(b)] = 1; }
	}
	for (int i = 0; i <n; i++)
	{
		if (mark[i] == 0)
		{
			head = i; break;
		}
	}
	levelorder();
	printf("\n");
	inorder(head);
}