C代碼不起作用

Question

/* 
* main.c 
* 
* Created on: Nov 30, 2012 
*  Author: mfb 
* 
*  Example input: 
*  5 5 2 2 0 0 
* y0 . . . . . 
* y1 a a a a . 
* y2 . . . a . 
* y3 . a a a . 
* y4 . . . . . 
* 
* x> 0 1 2 3 4 
*  I don't know why when I enter these to the program it comes to 4,4 and stops. 
*/ 

#include <stdio.h> 
int spx, spy, fx, fy, xsize, ysize; 

char *inmap, *check; 

int input(void) { 
    scanf(" %d %d %d %d %d %d", &xsize, &ysize, &fx, &fy, &spx, &spy); 
    inmap = (char *) malloc(xsize * ysize * sizeof(char)); 
    check = (char *) malloc(xsize * ysize * sizeof(char)); 

    int y; 
    for (y = 0; y < xsize * ysize; y++) 
     *(check + y) = 0; 

    char o; 
    for (y = 0; y < ysize * xsize; y++) { 
     scanf(" %c", &o); 
     if (o == '.') 
      *(inmap + y) = 1; 
     else 
      *(inmap + y) = 0; 
    } 
    return 0; 
} 

int itaw(char *map, int fpx, int fpy) { 
    if (*(check + fpy * xsize + fpx) == 1) 
     return 0; 
    else 
     *(check + fpy * xsize + fpx) = 1; 

    if (fpx >= xsize || fpy >= ysize || fpx < 0 || fpy < 0) 
     return 0; 

    if (*(map + fpy * xsize + fpx) == 0 || *(map + spy * xsize + spx) == 0) 
     return 0; 

    printf("(%d,%d)\n", fpx, fpy); 
    if (fpx == spx && fpy == spy) 
     return 1; 

    return (itaw(map, fpx - 1, fpy) || itaw(map, fpx, fpy - 1) 
      || itaw(map, fpx + 1, fpy) || itaw(map, fpx, fpy + 1)); 
} 

int main(void) { 
    input(); 
    int result = itaw(inmap, fx, fy); 
    printf("%d\n", result); 
    return 0; 
} 

上面是一個找到兩點之間方式的程序。 ''意味着方式和所有其他字符意味着一堵牆。 它主要工作，但當我輸入我上面寫的它返回0.

Answer 1

問題是，你沒有做訪問變量之前的邊界檢查。在訪問check之前，您必須確保它們大於0且小於最大值。我認爲這是正確的版本：

int itaw(char *map, int fpx, int fpy) { 
    if (fpx >= xsize || fpy >= ysize || fpx < 0 || fpy < 0) 
     return 0; 
    if (*(check + fpy * xsize + fpx) == 1) 
     return 0; 
    else 
     *(check + fpy * xsize + fpx) = 1;