我试图在400x200网格上实现BFS，该网格输入带有有序起始对和有序结束对的文本文件。我使用队列来跟踪打开的节点和数组以跟踪关闭的节点。我的程序在检查队列中打开的节点时，会在相同的输入上随机崩溃。
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
typedef struct Node Node;
typedef struct Qnode Qnode;
struct Node{
Node* up;
Node* down;
Node* left;
Node* right;
int xpos;
int ypos;
int marked;
};
struct Qnode{
Qnode* next;
Node* Gnode;
};
Qnode* front = NULL;
Qnode* rear = NULL;
int queuesize = 0;
int solutioncost = 0;
Node* closednodes[80000];
int nodesclosed = 0;
void enqueue(Node* node){
if (queuesize == 0){
rear = (Qnode*)malloc(sizeof(Qnode*));
rear->Gnode = node;
rear->next = NULL;
front = rear;
}
else{
Qnode* temp = (Qnode*)malloc(sizeof(Qnode*));
rear->next = temp;
temp->Gnode = node;
temp->next = NULL;
rear = temp;
}
queuesize++;
}
Node* dequeue(){
Qnode* temp = front;
if (queuesize == 0){
printf("Error!");
}
else{
Node* temp1 = front->Gnode;
temp = temp->next;
free(front);
front = temp;
queuesize--;
return temp1;
}
}
Node* generate(int x, int y){
printf("Generating node (%d,%d)...\n", x, y);
if ((x >0 && x <=400) && (y >0 && y <=200)){
Node* temp = (Node*)malloc(sizeof(Node));
temp->xpos = x;
temp->ypos = y;
temp->marked = 0;
temp->up = NULL;
temp->down = NULL;
temp->left = NULL;
temp->right = NULL;
return temp;
}
else{
printf("Invalid starting point! \n");
}
}
void expand(Node* node, int xend, int yend){
int flag = 0;
closednodes[nodesclosed] = node;
nodesclosed++;
dequeue();
if(node->marked == 1){
printf("already expanded");
}
else{
printf("Expanding node (%d, %d)...\n", node->xpos, node->ypos);
node->marked = 1;
if (node->xpos == xend && node->ypos == yend){
printf("Node reached!");
queuesize = 0;
return;
}
if (node->xpos-1 >0 && node->left == NULL){
int k = 0;
int j = 0;
Qnode* temp2 = front;
printf("%d", queuesize);
for(k; k<queuesize; k++){
int xx = temp2->Gnode->xpos;
int yy = temp2->Gnode->ypos;
printf("%d, %d,\n", xx, yy);
if (xx == node->xpos-1 && yy == node->ypos)
flag = 1;
temp2 = temp2->next;
}
for(j; j<nodesclosed; j++){
int xx = closednodes[j]->xpos;
int yy = closednodes[j]->ypos;
if (xx == node->xpos-1 && yy == node->ypos)
flag = 1;
}
if (flag == 0){
node->left = generate(node->xpos-1, node->ypos);
node->left->right = node->left;
enqueue(node->left);
}
else{
printf("(%d, %d) not generated.\n", node->xpos-1, node->ypos);
flag = 0;
}
}
if (node->xpos+1 <=400 && node->right ==NULL){
int k = 0;
int j = 0;
Qnode* temp2 = front;
for(k; k<queuesize; k++){
int xx = temp2->Gnode->xpos;
int yy = temp2->Gnode->ypos;
printf("%d, %d,\n", xx, yy);
if (xx == node->xpos+1 && yy == node->ypos)
flag = 1;
temp2 = temp2->next;
}
for(j; j<nodesclosed; j++){
int xx = closednodes[j]->xpos;
int yy = closednodes[j]->ypos;
if (xx == node->xpos+1 && yy == node->ypos)
flag = 1;
}
if (flag == 0){
node->right = generate(node->xpos+1, node->ypos);
node->right->left = node->right;
enqueue(node->right);
}
else{
printf("(%d, %d) not generated.\n", node->xpos+1, node->ypos);
flag = 0;
}
}
if (node->ypos+1 <=200 && node->up ==NULL){
int k = 0;
int j = 0;
Qnode* temp2 = front;
printf("%d", queuesize);
for(k; k<queuesize; k++){
int xx = temp2->Gnode->xpos;
int yy = temp2->Gnode->ypos;
if (xx == node->xpos && yy == node->ypos+1)
flag = 1;
temp2 = temp2->next;
}
for(j; j<nodesclosed; j++){
int xx = closednodes[j]->xpos;
int yy = closednodes[j]->ypos;
if (xx == node->xpos && yy == node->ypos+1)
flag = 1;
}
if (flag ==0){
node->up = generate(node->xpos, node->ypos+1);
node->up->down = node->up;
enqueue(node->up);
}
else{
printf("(%d, %d) not generated.\n", node->xpos, node->ypos+1);
flag = 0;
}
}
if (node->ypos-1 >0 && node->down ==NULL){
int k = 0;
int j = 0;
Qnode* temp2 = front;
for(k; k<queuesize; k++){
int xx = temp2->Gnode->xpos;
int yy = temp2->Gnode->ypos;
printf("%d, %d,\n", xx, yy);
if (xx == node->xpos && yy == node->ypos-1)
flag = 1;
temp2 = temp2->next;
}
for(j; j<nodesclosed; j++){
int xx = closednodes[j]->xpos;
int yy = closednodes[j]->ypos;
if (xx == node->xpos && yy == node->ypos-1)
flag = 1;
}
if (flag ==0){
node->down = generate(node->xpos, node->ypos-1);
node->down->up = node->down;
enqueue(node->down);
}
else{
printf("(%d, %d) not generated.\n", node->xpos, node->ypos-1);
flag = 0;
}
}
printf("EXPANSION ENDS\n");
return;
}
}
int main(){
int x_start, y_start, x_end, y_end;
FILE *fp;
fp = fopen("testfile.txt", "r");
if (fp == NULL)
printf("Error printing output. \n");
else
fscanf(fp, "(%d,%d)\n", &x_start, &y_start);
fscanf(fp, "(%d,%d)\n", &x_end, &y_end);
printf("Starting point is (%d, %d)\n", x_start, y_start);
printf("Ending point is (%d, %d)\n", x_end, y_end);
Node* start = generate(x_start, y_start);
enqueue(start);
while(queuesize!=0){
expand(front->Gnode, x_end, y_end);
}
fclose(fp);
}
使用testfile.txt
(1,1)
(50,50)
此输入将导致程序随机崩溃。我怀疑我的队列有问题。
答案 0 :(得分：2)
在enqueue函数中，您应该将新节点分配为（Qnode *）malloc（sizeof（ Qnode ））（而不是（Qnode *））。你编写的代码只为每个结构分配一个指针的大小，所以对这样一个对象的任何写操作都会踩到其他对象的内存。