本题要求给定二叉树的4种遍历。

函数接口定义：

void InorderTraversal( BinTree BT );
void PreorderTraversal( BinTree BT );
void PostorderTraversal( BinTree BT );
void LevelorderTraversal( BinTree BT );

其中BinTree结构定义如下：

typedef struct TNode *Position;
typedef Position BinTree;
struct TNode{
    
    ElementType Data;
    BinTree Left;
    BinTree Right;
};

``要求4个函数分别按照访问顺序打印出结点的内容，格式为一个空格跟着一个字符。

裁判测试程序样例：

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

typedef char ElementType;
typedef struct TNode *Position;
typedef Position BinTree;
struct TNode{
    
    ElementType Data;
    BinTree Left;
    BinTree Right;
};

BinTree CreatBinTree(); /* 实现细节忽略 */
void InorderTraversal( BinTree BT );
void PreorderTraversal( BinTree BT );
void PostorderTraversal( BinTree BT );
void LevelorderTraversal( BinTree BT );

int main()
{
    
    BinTree BT = CreatBinTree();
    printf("Inorder:");    InorderTraversal(BT);    printf("\n");
    printf("Preorder:");   PreorderTraversal(BT);   printf("\n");
    printf("Postorder:");  PostorderTraversal(BT);  printf("\n");
    printf("Levelorder:"); LevelorderTraversal(BT); printf("\n");
    return 0;
}
/* 你的代码将被嵌在这里 */
输出样例（对于图中给出的树）：


Inorder: D B E F A G H C I
Preorder: A B D F E C G H I
Postorder: D E F B H G I C A
Levelorder: A B C D F G I E H

解答

void InorderTraversal( BinTree BT ){
    
    if(BT == NULL) return;
    InorderTraversal(BT->Left);
    printf(" %c",BT->Data);
    InorderTraversal(BT->Right);

}
void PreorderTraversal( BinTree BT ){
    
    if(BT == NULL) return;
    printf(" %c",BT->Data);
    PreorderTraversal(BT->Left);
    PreorderTraversal(BT->Right);

}
void PostorderTraversal( BinTree BT ){
    
    if(BT == NULL) return;
    PostorderTraversal(BT->Left);
    PostorderTraversal(BT->Right);
    printf(" %c",BT->Data);
}

/*typedef struct QNode{ BinTree data[100]; int base , top; }QNode,*queue; queue initqueue(){ queue q = (queue) malloc(sizeof (QNode)); q->base = 0; q->top = 0; return q; } void pop(queue q){ if(q->top != q->base) q->base++; } BinTree front(queue q){ return q->data[q->base]; } void push(queue q,BinTree e){ if(q->top < 100){ q->data[q->top++] = e; } } int size(queue q){ return q->top - q->base; } typedef enum {false,true} bool; bool isEmpty(queue q){ return q->base == q->top?true:false; } void LevelorderTraversal( BinTree BT ){ if(BT == NULL) return ; queue q = initqueue(); push(q,BT); while (!isEmpty(q)){ int count = size(q); for(int i = 0;i<count;i++){ BinTree tree = front(q); printf("%c ",tree->Data); pop(q); if(tree ->Left!=NULL) push(q,tree->Left); if(tree -> Right != NULL) push(q,tree->Right); } } }*/
void LevelorderTraversal( BinTree BT ) {
    
    if (BT == NULL) return;
    BinTree queue[100];
    int base = 0;
    int front = 0;
    //queue q = initqueue();
   // push(q, BT);
   queue[front++] = BT;
    while (base<front) {
    
        int count = front - base;
        for (int i = 0; i < count; i++) {
    
            BinTree tree = queue[base];
            printf(" %c", tree->Data);
            base++;
            if (tree->Left != NULL) queue[front++] = tree ->Left;
            if (tree->Right != NULL) queue[front++] = tree ->Right;
        }
    }
}

完整的程序

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


typedef char ElementType;
typedef struct TNode *Position;
typedef Position BinTree;
struct TNode{
    
    ElementType Data;
    BinTree Left;
    BinTree Right;
};

BinTree CreatBinTree(); /* 实现细节忽略 */
void InorderTraversal( BinTree BT );
void PreorderTraversal( BinTree BT );
void PostorderTraversal( BinTree BT );
void LevelorderTraversal( BinTree BT );

int main()
{
    
    freopen("/root/tmp/c_data_structure/std.in","r", stdin);
    BinTree BT = CreatBinTree();
    printf("Inorder:");    InorderTraversal(BT);    printf("\n");
    printf("Preorder:");   PreorderTraversal(BT);   printf("\n");
    printf("Postorder:");  PostorderTraversal(BT);  printf("\n");
    printf("Levelorder:"); LevelorderTraversal(BT); printf("\n");
    return 0;
}
/* 你的代码将被嵌在这里 */
BinTree CreatBinTree() {
    
    ElementType dada;
    scanf("%c",&dada);
    if(dada =='-'){
    
        return NULL;
    }
    BinTree root = (BinTree) malloc(sizeof (struct TNode));
    root->Data = dada;
    root->Left = CreatBinTree();
    root->Right = CreatBinTree();
    return root;
}

void InorderTraversal( BinTree BT ){
    
    if(BT == NULL) return;
    InorderTraversal(BT->Left);
    printf(" %c",BT->Data);
    InorderTraversal(BT->Right);

}
void PreorderTraversal( BinTree BT ){
    
    if(BT == NULL) return;
    printf(" %c",BT->Data);
    PreorderTraversal(BT->Left);
    PreorderTraversal(BT->Right);

}
void PostorderTraversal( BinTree BT ){
    
    if(BT == NULL) return;
    PostorderTraversal(BT->Left);
    PostorderTraversal(BT->Right);
    printf(" %c",BT->Data);
}

/*typedef struct QNode{ BinTree data[100]; int base , top; }QNode,*queue; queue initqueue(){ queue q = (queue) malloc(sizeof (QNode)); q->base = 0; q->top = 0; return q; } void pop(queue q){ if(q->top != q->base) q->base++; } BinTree front(queue q){ return q->data[q->base]; } void push(queue q,BinTree e){ if(q->top < 100){ q->data[q->top++] = e; } } int size(queue q){ return q->top - q->base; } typedef enum {false,true} bool; bool isEmpty(queue q){ return q->base == q->top?true:false; } void LevelorderTraversal( BinTree BT ){ if(BT == NULL) return ; queue q = initqueue(); push(q,BT); while (!isEmpty(q)){ int count = size(q); for(int i = 0;i<count;i++){ BinTree tree = front(q); printf("%c ",tree->Data); pop(q); if(tree ->Left!=NULL) push(q,tree->Left); if(tree -> Right != NULL) push(q,tree->Right); } } }*/
void LevelorderTraversal( BinTree BT ) {
    
    if (BT == NULL) return;
    BinTree queue[100];
    int base = 0;
    int front = 0;
    //queue q = initqueue();
   // push(q, BT);
   queue[front++] = BT;
    while (base<front) {
    
        int count = front - base;
        for (int i = 0; i < count; i++) {
    
            BinTree tree = queue[base];
            printf(" %c", tree->Data);
            base++;
            if (tree->Left != NULL) queue[front++] = tree ->Left;
            if (tree->Right != NULL) queue[front++] = tree ->Right;
        }
    }
}