03-树2 List Leaves（25 分）/C

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 <stdio.h>
#include <stdlib.h>

#define MaxTree 10
#define Null -1
typedef char ElementType;
typedef int Tree;
struct TreeNode
{	Tree Left,Right;
}T[MaxTree];

struct Node
{	ElementType Element;
	struct Node* Next;
};

typedef struct QNode* QueueNode;
struct QNode
{	struct Node *Front;
	struct Node *Rear;
};

Tree BuildTree(struct TreeNode T[]);
void SearchLeaves(int Root);
QueueNode CreateQueue(int);//要求从上至下，从左至右 = 层次遍历
QueueNode AddQ(QueueNode,int);//入队
ElementType DeleteQ();//离队

int main()
{
	int Root = BuildTree(T);
	SearchLeaves(Root);
	return 0;
}


Tree BuildTree(struct TreeNode T[])
{
	int n=0,c[MaxTree];
	char tl,tr;
	int i,Root=Null;
	scanf("%d",&n);
	if(n)
	{	
		for (i=0; i<n; i++) c[i] = 0;
		for (i=0; i<n; i++) 
		{
			scanf("\n%c %c",&tl, &tr);
			if (tl != '-') 
			{
				T[i].Left = tl-'0';
				c[T[i].Left] = 1;
			}
			else 
				T[i].Left = Null;
			if (tr != '-')
			{
				T[i].Right = tr - '0';
				c[T[i].Right] = 1;
			}
			else
				T[i].Right = Null;
		}
		for(i=0;i<n;i++)
			if(!c[i]) break;
		Root = i;
	}
	return Root;
}

QueueNode CreateQueue()
{
	QueueNode PtrQ = (QueueNode)malloc(sizeof(struct QNode));
	PtrQ->Front = PtrQ->Rear = NULL;
	return PtrQ;
}

QueueNode AddQ(QueueNode Q,int X)
{
	struct Node* temp = (struct Node*)malloc(sizeof(struct Node));
	temp->Element = X;
	temp->Next = NULL;
	if(Q->Front == NULL)
	{
		Q->Front = temp;
		Q->Rear = Q->Front;
	}
	else
	{
		Q->Rear->Next = temp;
		Q->Rear = temp;
	}
	return Q;
}
ElementType DeleteQ(QueueNode Q)
{
	struct Node* temp;
	int X;
	if(Q->Front == NULL)
		return Null;
	temp = Q->Front;
	X = Q->Front->Element;
	if(Q->Front == Q->Rear)
		Q->Front = Q->Rear = NULL;
	else
		Q->Front = Q->Front->Next;
	free(temp);
	return X;
}

void SearchLeaves(int Root)//层次遍历
{
	int flag = 0;
	QueueNode Q = CreateQueue();
	AddQ(Q, Root);//加入根节点
	while (Q->Front)//扫描树
	{
		Root = DeleteQ(Q);
		if(T[Root].Left == Null && T[Root].Right == Null)
		{
			if(flag) printf(" %d",Root);
			else 
			{
			        printf("%d",Root);
			        flag = 1;
			}
		}
		else if(T[Root].Left !=Null && T[Root].Right == Null)
			AddQ(Q,T[Root].Left);
		else if(T[Root].Left ==Null && T[Root].Right != Null)
			AddQ(Q,T[Root].Right);
		else
		{	
			AddQ(Q,T[Root].Left);
			AddQ(Q,T[Root].Right);
		}
	}
}