找不到这个简单的 C 代码有什么问题

Question

简单的树插入遍历代码

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

struct tree
{
    struct tree *left;
    struct tree *right;
    int value;
};

typedef struct tree node;

void insertNode(node **root, int val)
{
    node *temp = NULL;
    if(!(*root))
    {
        temp = (node*) malloc(sizeof(node));
        temp->value = val;
        temp->left = NULL;
        temp->right = NULL;
        *root = temp;
    }

    if(val < (*root)->value)
        insertNode(&(*root)->left, val);

    if(val >= (*root)->value)
        insertNode(&(*root)->right, val);
}

void preOrder(node *root)
{
    if(root)
    {   printf(" %d",root->value);
        preOrder(root->left);
        preOrder(root->right);
    }
}

void inOrder(node *root)
{
    if(root)
    {
        inOrder(root->left);
        printf(" %d",root->value);
        inOrder(root->right);
    }
}

void postOrder(node *root)
{
    if(root)
    {
        postOrder(root->left);
        postOrder(root->right);
        printf(" %d",root->value);
    }
}

void delTree(node *root)
{
    if(root)
    {
        delTree(root->left);
        delTree(root->right);
        free(root);
    }
}

int main()
{
    int val;
    char ch; ch = 'y';
    node *root;

    while(ch == 'y')
    {
        scanf("Enter the node value: %d", &val);
        insertNode(&root, val);
        scanf("Want to enter more: %c", &ch);
    }

    printf("\nInOrder traversal:\n");
    inOrder(root);
    printf("\nPreOrder traversal:\n");
    preOrder(root);
    printf("\nPostOrder traversal:\n");
    postOrder(root);

    delTree(root);
    printf("Tree Deleted.");

    return 0;
}

代码好像没有问题，也没有报错。虽然编译时显示警告；

ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute

这似乎是由于忽略了 scanf 的 return 值而启动的，来自 ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]? .

但即使在抑制警告和编译可执行文件时也没有接受任何输入。这是为什么。我在 CodeBlocks IDE.

上运行代码

ideone也是一样，http://ideone.com/jOnjEK .

如有任何帮助或建议，我们将不胜感激。

Answer 1

scanf("Enter the node value: %d", &val);应该是

scanf("%d", &val);

和

scanf("Want to enter more: %c", &ch);应该是

scanf(" %c", &ch);

假设您打算这样做

printf("Enter the node value:\n");
if(scanf("%d", &val) != 1)
{
printf("Integer not read \n");
break;
} 

printf("Want to enter more:\n");
if(scanf(" %c", &ch) != 1)
{
printf("character not read\n");
break;
}

记下 scanf()

中 %c 之前的 space

找不到这个简单的 C 代码有什么问题

Can't find what's wrong with this simple C code

c

binary-search-tree

scanf

gcc-warning