0

I am not too good at making trees and I totally screw up recursion. However, I attempted to make a program to insert and display data into the tree.

The problem is that it crashes after inserting into the root node and I do not know why. The tree is not too big. Just 10 int. 

#include <stdio.h>
#include <stdlib.h>
#define SIZE 10;
/* run this program using the console pauser or add your own getch, system("pause") or input loop */
struct node{
    int data;
    struct node * left;
    struct node * right;
};


void insert(struct node * root,int num){
    printf("Insert called for num:%d\n",num);
    if(root == NULL){
        root = (struct node *)malloc(sizeof(struct node));
        root->data = num;
    }else if(num > root->data){ // Number greater than root ?
        insert(root->right,num); // Let the right sub-tree deal with it
    }else if(num < root->data){// Number less than root ?
        insert(root->left,num);// Let the left sub-tree deal with it.
    }else{
        // nothing, just return.
    }
}


void display(struct node * root){ // Inorder traversal
    if(root->left!=NULL){ // We still have children  in left sub-tree ?
        display(root->left); // Display them.
    }

    printf("%d",root->data); // Display the root data

    if(root->right!=NULL){ // We still have children in right sub-tree ?
        display(root->right); // Display them.
    }

}

int main(int argc, char *argv[]) {
    int a[10] = {2,1,3,5,4,6,7,9,8,10};
    int i;
    struct node * tree;

    for(i = 0; i < 10;i++){
        insert(tree,a[i]);
    }
    printf("Insert done");
    return 0;
}

Can someone please tell me where I went wrong ?

I know it is frowned upon to ask people to review your code on Stack but sometimes pair programming works :p

Update:
After setting struct node * tree = NULL;, the insert() method works well. The display() causes program to crash.

4

1 回答 1

2

在你的

int main(int argc, char *argv[]) {
    // ...
    struct node * tree;
    // what is the value of tree at this line?
    for(i = 0; i < 10;i++){
        insert(tree,a[i]);
    }
    // ...
}

“树”在标记的线上指向什么？

于 2013-10-02T04:57:49.537 回答