03-树2 List Leaves

 

坚持！量变引起质变！

03-树2 List Leaves （25 分）

Given a tree, you are supposed to list all the leaves in the order of top down, and left to right.

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, 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 one line all the leaves' indices in the order of top down, and left to right. 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

4 1 5

#include<iostream>
using namespace std;
#define Null -1;
typedef struct Node Tree;
struct Node {
	int left;
	int right;
	int tag;   //tag == 1 ,leaf
}T[10];

typedef struct QNode *Queue;
struct QNode {
	int *data;
	int pre, rear;
	int MaxSize;
};

Queue CreateQueue(int MaxSize) {
	Queue q = (Queue)malloc(sizeof(struct QNode));
	q->data = (int *)malloc( MaxSize * sizeof(int) );
	q->pre = NULL;
	q->rear = NULL;
	q->MaxSize = MaxSize;
	return q;
}

bool IsFull(Queue q) {
	return (
		(q->rear + 1) % q->MaxSize == q->pre
		);
}
bool AddQueue(Queue q, int n) {
	if (!IsFull(q)) {
		q->rear = (q->rear + 1) % q->MaxSize;
		q->data[q->rear] = n;
		return true;
	}
	else
		return false;
}

bool IsEmpty(Queue q) {
	return (
		q->pre == q->rear
		);
}

int DeleteQueue(Queue q) {
	if (!IsEmpty(q))
	{
		q->pre = (q->pre + 1) % q->MaxSize;
		return (q->data[q->pre]);
	}
	else
		return -1;
}
int BuildTree(int n) {
	int root = -1;
	char cl, cr;
	int check[10] = {0};   //check[i] == 0 即为根
	for(int i = 0; i< n ;i ++)
		{
		cin >> cl >> cr;
		if (cl != '-')
		{
			T[i].left = cl - '0';
			check[T[i].left] = 1;
		}
		else
			T[i].left = Null;
		if (cr != '-')
		{
			T[i].right = cr - '0';
			check[T[i].right] = 1;
		}
		else
			T[i].right = Null;
		if ((T[i].right == -1) && (T[i].left == -1))
			T[i].tag = 1;    //tag = 1 ,leaf
		else
			T[i].tag = 0;
	}
	for (int i = 0; i < n; i++) {
		if (check[i] == 0)
		{
			root = i;
			break;
		}
	}
	return root;
}

void ListLeaves(Tree T[], int N, int Root) {
	Queue Q;
	Q = CreateQueue(10);
	int i = 0;
	int out[10] = {-1};  //使用out进行存储和输出
	int *p = out;
	for (i = 0; i < 10; i++) {
		out[i] = -1;
	}
	AddQueue(Q, Root);   //add indices into the queue
	for (i = 0; !IsEmpty(Q);) {
		i = DeleteQueue(Q);
		if (T[i].tag == 1)
		{
			*p= i;
			p++;
		}
		if (T[i].left != -1)   AddQueue(Q, T[i].left);
		if (T[i].right != -1)  AddQueue(Q, T[i].right);
	}
	for ( i = 0; i < N; i++) {
		if (out[i + 1] != -1)
			cout << out[i] << ' ';
		else
		{
			cout << out[i];
			break;
		}
	}
}

int main() {
	int N,Root;  //N is the number of Nodes
	cin >> N;
	Root = BuildTree(N);
	ListLeaves(T,N,Root);

	return 0;
}

 建树->建队列->将两者联合起来，真不容易，看着别人写的程序很简单，自己写的时候才知道这里面有多少坑！加油！