我的链表有问题。这是一个带有双重列表的蛇游戏，它不应该吃东西，它只是每 5 步增长 1 个街区

Question

• 我的链表有问题。
• 这是一个带有双重列表的贪吃蛇游戏，它不应该吃东西，它只是每 5 步增长 1 块。
• 这是一个带有双重列表的贪吃蛇游戏，它不应该吃东西，它只是每 5 步增长 1 块。 我在蛇初始函数中得到"取消引用空点"，读取访问违规。蛇尾Ptr 0xCDCDCDCD。无效打印功能
• 列表项

#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
#include <conio.h>
#include <stdlib.h>
#include <time.h>
#include <stdbool.h>
#define ROWS 25
#define COLS 75
// terminal escape codes/ANSI escape codes (or ANSI escape sequences)
// "x1B" is the escape character that tells your terminal that what comes next is not meant to be printed on the screen, 
// but rather a command to the terminal (or most likely terminal emulator).
// Turn escape codes ON.
// Turn escape codes ON.
typedef struct node {
int x;
int y;
struct node* next;
struct node* prev;
}NODE;
typedef struct SNAKE {
NODE* head;
NODE* tail;
}SNAKE;
// Moves the cursor to position (x,y) on screen.
// Parameters:
//     x: the row of the position.
//     y: the column of the position.
void gotoxy( int x, int y );
// Delays the execution of the program.
// Parameters:
//     secs: the length of the delay in seconds. 
void sleep( float secs );
//My Functions///
void init( void );
void print( SNAKE* snake );
void initialTheBoard( char board[ROWS][COLS] );//Initial the board limits and print them
void initialSnaKE( SNAKE* snake );//initial the snake in the middle
void snakeSpeed( float* delay, int counter );
void checkInput( SNAKE* snake, char* keystoke, char* lastmove, int * newX, int * newY );//Check if to change the snake direction
void SnakeMovment( SNAKE* snake, int counter, float* delay, int newX, int newY, char board[ROWS][COLS] );//move the snake
bool checkIfGameOver( SNAKE* snake, char matrix[ROWS][COLS], int newX, int newY );//check if the game is over
void GameOverPrint( char board[ROWS][COLS] );//Print game over in the middle of the screen when the player lose 
void printBoard( char board[ROWS][COLS] );
int main() {
//variables that will be used in the game
float delay = 1.000;
int newX = 0, newY = 0;
int x = ROWS / 2, y = COLS / 2, count = 0;;
bool gameOver = false;
char keystroke = 'd', lastmove = 'd';
char Boardmatrix[ROWS][COLS];
//intial the snake and put him in the middle
SNAKE* snake = (SNAKE*)malloc( sizeof( SNAKE ) );
initialSnaKE( snake );
initialTheBoard( Boardmatrix );
//The Game
while ( gameOver == false )
{
init();
printBoard( Boardmatrix );
print( snake );
count++;
_kbhit();
keystroke = _getch();
checkInput( snake, &keystroke, &lastmove, &newX, &newY );
gameOver = checkIfGameOver( snake, Boardmatrix, newX, newY );
SnakeMovment( snake, count, &delay, newX, newY, Boardmatrix );
snakeSpeed( &delay, count );
sleep( delay );
}
GameOverPrint( Boardmatrix );
}
void initialSnaKE( SNAKE* snake )//maybe x,y of tail need to be different
{
//Snake start in the middle with the right values
//Need to add malloc
NODE* newNode = (NODE*)malloc( sizeof( NODE ) );
newNode->x = ROWS / 2;
newNode->y = COLS / 2;
snake->head = newNode;
snake->tail = newNode;
snake->head->prev = NULL;
snake->head->next = NULL;
}
void initialTheBoard( char board[ROWS][COLS] )
{
for ( int i = 0; i < ROWS; i++ ) {
for ( int j = 0; j < COLS; j++ ) {
board[i][j] = ' ';
}
}
for ( int i = 0; i < ROWS; i++ ) {
board[i][0] = '#';
board[i][COLS - 1] = '#';
}
for ( int i = 0; i < COLS; i++ ) {
board[0][i] = '#';
board[ROWS - 1][i] = '#';
}
}
void printBoard( char board[ROWS][COLS] ) {
for ( int i = 0; i < ROWS; i++ ) {
for ( int j = 0; j < COLS; j++ ) {
printf( "%c", board[i][j] );
}
printf( "n" );
}
}
void checkInput( SNAKE * snake, char* keystoke, char* lastmove, int* newX, int* newY )
{
if ( *lastmove != 's' && *keystoke == 'w' ) {
snake->head->x = snake->head->x - 1;
*newX = -1;
*newY = 0;
*lastmove = 'w';
}
else if ( *lastmove != 'w' && *keystoke == 's' ) {
snake->head->x = snake->head->x + 1;
*lastmove = 's';
*newX = 1;
*newY = 0;
}
else if ( *lastmove != 'a' && *keystoke == 'd' ) {
snake->head->y = snake->head->y + 1;
*lastmove = 'd';
*newX = 0;
*newY = 1;
}
else if ( *lastmove != 'd' && *keystoke == 'a' ) {
snake->head->y = snake->head->y - 1;
*lastmove = 'a';
*newX = 0;
*newY = -1;
}
else {
if ( *lastmove == 'a' ) {
snake->head->y = snake->head->y - 1;
*newX = 0;
*newY = -1;
}
if ( *lastmove == 'd' ) {
snake->head->y = snake->head->y + 1;
*newX = 0;
*newY = 1;
}
if ( *lastmove == 'w' ) {
snake->head->x = snake->head->x - 1;
*newX = -1;
*newY = 0;
}
if ( *lastmove == 's' ) {
snake->head->x = snake->head->x + 1;
*newX = 1;
*newY = 0;
}
}
}
void SnakeMovment( SNAKE* snake, int counter, float* delay, int newX, int newY, char board[ROWS][COLS] ) {
/*
if (counter < 5) {
print(snake);
}*/
//else {
NODE* newHead = (NODE*)(malloc( sizeof( NODE ) ));
NODE* oldHead = (NODE*)(malloc( sizeof( NODE ) ));
newHead->x = snake->head->x + newX;
newHead->y = snake->head->y + newY;
oldHead = snake->head;
snake->head = newHead;
snake->head->next = oldHead;
oldHead->prev = snake->head;
board[snake->head->x][snake->head->y] = '@';
/*
if (counter % 5 != 0) {
board[snake->tail->x][snake->tail->y] = ' ';
NODE* oldTail;
oldTail = snake->tail->prev;
snake->tail->prev = oldTail->prev;
free(oldTail);
}
print(snake);
}*/
}
void snakeSpeed( float *delay, int counter )
{
if ( *delay > 100 && counter % 5 == 0 )
{
*delay -= (float)0.300;
}
}

// Turn escape codes ON.
void init( void ) {
system( "cls" );
}


bool checkIfGameOver( SNAKE* snake, char matrix[ROWS][COLS], int newX, int newY )
{
int theX = snake->head->x, theY = snake->head->y;
if ( matrix[theX + newX][theY + newY] != ' ' ) {
return true;
}
else {
return false;
}
}
void print( SNAKE* snake ) {
NODE* snakeTailPtr = snake->tail;
while ( snakeTailPtr != NULL ) {
gotoxy( snakeTailPtr->x, snakeTailPtr->y );
snakeTailPtr = snakeTailPtr->prev;
printf( "@" );
}
}

void GameOverPrint( char board[ROWS][COLS] )//need to add board clean
{
initialTheBoard( board );
char gameOverMessage[10] = "Game Over";
int j = 0;
int middleCol = (COLS / 2);
for ( int i = middleCol - 4; i <= middleCol + 4; i++ ) {
board[ROWS / 2][i] = gameOverMessage[j];
j++;
}
printBoard( board );
for ( int i = 0; i < ROWS; i++ ) {
printf( "n" );
}
}
// Moves the cursor to position (x,y) on screen.
// Parameters:
//     x: the row of the position.
//     y: the column of the posiiton.
void gotoxy( int x, int y ) {
printf( "x1b[%d;%df", x, y );
}

void sleep( float secs ) {
clock_t clocks_start = clock();
while ( clock() - clocks_start < secs * CLOCKS_PER_SEC );
}

Answer 1

在程序上使用调试器时，我发现问题出在函数SnakeMovement中。

在该函数中，您可以初始化结构成员变量x、y和nextnewHead，但不初始化结构成员变量prev。这就是为什么它稍后在函数print中访问时具有未初始化的值 0xCDCDCDCD ，这在取消引用时会导致访问冲突。您可能希望在函数SnakeMovement中使用值 NULL 初始化此变量，以便函数print中的循环可以检测到已到达列表的末尾。

此外，函数的以下行SnakeMovement创建内存泄漏：

NODE* oldHead = (NODE*)(malloc( sizeof( NODE ) ));
[...]
oldHead = snake->head;

首先，将动态分配的内存的地址分配给oldHead，但随后用其他值覆盖该变量，以便分配的内存永远不会被释放(甚至使用(。如果您永远不需要内存，则不应分配它。