c - 红黑树书实现(SIGSEGV发生)

Question

我正在尝试根据我的大学书籍编写标题算法的实现。我已经编写了最重要的函数，但最终程序崩溃了。 GDB在线调试器指向第91行程序收到信号 SIGSEGV，段错误。 0x0000000000400ac4 in RB_Insert (T=0x0, k=5) at main.c:90 90 while((X != root) && (X->up->color == 'R')){

5 是我尝试插入的第一个值，所以我想知道为什么语句 X != root 不会阻止它并且打印 sigsegv

我将在此处粘贴整个代码:

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

struct node{
    int key;
    char color;
    struct node *up;
    struct node *left;
    struct node *right;
}*root;


void in_order_tree_walk(struct node *X){
    if(X!=NULL){
        in_order_tree_walk(X->left);
        printf("%d %c\n", X->key, X->color);
        in_order_tree_walk(X->right);
    }
}

struct node* tree_search(struct node *X, int k){
    if(X==NULL || k==X->key)
        return X;
    if(k<X->key)
        return tree_search(X->left, k);
    else
        return tree_search(X->right, k);
}

struct node* tmp_node(int k){
    struct node *tmp = (struct node*)malloc(sizeof *root);
    tmp->up = NULL;
    tmp->left = NULL;
    tmp->right = NULL;
    tmp->key = k;
    tmp->color = 'R';
    return tmp;
}

void tree_insert(struct node *T, struct node *Z){
    if (T == NULL){
        T = Z;
        return;
    }
    else{
        if (Z->key < T->key){
        tree_insert(T->left, Z);
        T->left->up = T;
    }
    else if (Z->key > T->key){
        tree_insert(T->right,Z);
        T->right->up = T;
    }
  }
}

void left_rotate(struct node *X){
    struct node *Y = X->right;
    X->right = Y->left;
    if(Y->left != NULL)
        Y->left->up = X;
    Y->up = X->up;
    if(X->up == NULL)
        root = Y;
    else if( X == X->up->left)
        X->up->left = Y;
        else X->up->right = Y;
    Y->left = X;
    X->up = Y;
}

void right_rotate(struct node *X){
    struct node *Y = X->left;
    X->left = Y->right;
    if(Y->right != NULL)
        Y->right->up = X;
    Y->up = X->up;
    if(X->up == NULL)
        root = Y;
    else if( X == X->up->left)
        X->up->left = Y;
    else X->up->right = Y;
    Y->right = X;
    X->up = Y;
}

void RB_Insert(struct node *T, int k){
    struct node *X = tmp_node(k);
    tree_insert(T, X);
    X->color = 'R';
    while(X != root && X->up->color == 'R'){
        if(X->up = X->up->up->left){
            struct node *Y = X->up->up->right;
            if(Y->color == 'R'){
                X->up->color = 'B';
                Y->color = 'B';
                X->up->up->color = 'R';
                X = X->up->up;
            }
            else{
                if (X == X->up->right){
                X = X->up;
                left_rotate(X);

                }
                X->up->color = 'B';
                X->up->up->color = 'R';
                right_rotate(X->up->up);
            }
        }
        else{
            struct node *Y = X->up->up->left;
            if(Y->color == 'R'){
                X->up->color = 'B';
                Y->color = 'B';
                X->up->up->color = 'R';
                X = X->up->up;
            }
            else{
                if (X == X->up->left){
                X = X->up;
                right_rotate(X);
                }
                X->up->color = 'B';
                X->up->up->color = 'R';
                left_rotate(X->up->up);
            }
        }
    }
    root->color = 'B';
}

int main(){

    root = NULL; 
    int T[] = {5,26,17,8,9,30,10,1,23};
    int i;
    for(i=0; i<9; i++){
        printf("%d", T[i]);
        RB_Insert(root, T[i]);
    }
    printf("\n");
    in_order_tree_walk(root);

    return 0;
}

Answer 1

我将tree_insert更改为

struct node *Y = NULL;
    struct node *X = root;
    while(X != NULL)
    {
        Y = X;
        if(Z->key < X->key) X=X->left;
        else X=X->right;
    }
    Z->up = Y;
    if( Y == NULL)
    root = Z;
    else if(Z->key < Y->key) Y->left = Z;
    else Y->right = Z;

并在第 114 行添加了 if 语句 if(Y != NULL && Y->color == 'R'){ 现在工作正常