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 $N$ ($\le 10$) 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:

81 -- -0 -2 7- -- -5 -4 6

Sample Output:

4 1 5

#include <stdio.h>#include <stdlib.h>#define MaxTree 10#define Null -1#define ERROR -1typedef char ElementType;typedef int Tree;struct TreeNode {ElementType element;Tree Left, Right;}T[MaxTree];struct Node{ElementType Data;struct Node *Next;};typedef struct QNode *QueueNode;struct QNode{struct Node *Front;struct Node *Rear;};Tree BuildTree(struct TreeNode T[]);void SearchLeaves(Tree Root);QueueNode CreateQueue();int QIsEmpty(QueueNode PtrQ);QueueNode AddQ(QueueNode PtrQ, ElementType ElemX);ElementType DeleteQ(QueueNode PtrQ);int main(){Tree R;R = BuildTree(T);SearchLeaves(R);system("pause");return 0;}Tree BuildTree(struct TreeNode T[]){int N = 0;Tree Root = Null;int check[MaxTree] = { 0 };char cl, cr;scanf("%d", &N);getchar();for (int i = 0; i < N; i++){T[i].element = i;scanf("%c %c", &cl, &cr);getchar();if (cl != '-'){T[i].Left = cl - '0';check[T[i].Left] = 1;}elseT[i].Left = Null;if (cr != '-'){T[i].Right = cr - '0';check[T[i].Right] = 1;}elseT[i].Right = Null;}for (int i = 0; i < N; i++){if (!check[i]){Root = i;break;}}return Root;}void SearchLeaves(Tree Root){int i = 0;int flag = 1;QueueNode Q = CreateQueue();AddQ(Q, Root);while (!QIsEmpty(Q)){Root = DeleteQ(Q);if (T[Root].Left == Null &&T[Root].Right == Null){if (flag){printf("%d", Root);flag = 0;}elseprintf(" %d", Root);}if (T[Root].Left != Null)AddQ(Q, T[Root].Left);if (T[Root].Right != Null)AddQ(Q, T[Root].Right);}}QueueNode CreateQueue(){QueueNode PtrQ = (QueueNode)malloc(sizeof(struct QNode));PtrQ->Front = PtrQ->Rear = NULL;return PtrQ;}int QIsEmpty(QueueNode PtrQ){if (PtrQ->Front == NULL)return 1;else return 0;}QueueNode AddQ(QueueNode PtrQ, ElementType ElemX){struct Node *tmp = (struct Node*)malloc(sizeof(struct Node));tmp->Data = ElemX;if (QIsEmpty(PtrQ)){PtrQ->Front = tmp;PtrQ->Rear = tmp;}else{PtrQ->Rear->Next = tmp;PtrQ->Rear = tmp;}return PtrQ;}ElementType DeleteQ(QueueNode PtrQ){struct Node *FrontCell;ElementType ElemX;if (PtrQ->Front == NULL){printf("队列为空");return ERROR;}FrontCell = PtrQ->Front;ElemX = PtrQ->Front->Data;if (PtrQ->Front == PtrQ->Rear)PtrQ->Front = PtrQ->Rear = NULL;elsePtrQ->Front = PtrQ->Front->Next;free(FrontCell);return ElemX;}