C语言，邻接矩阵

Question

在您的帮助下，我可以从文本文件(input.txt)中获取输入，其中各行由 city1 city2 距离组成...并将城市名称写入矩阵中而不重复。根据这个矩阵我写了一段代码来将它们的距离添加到邻接矩阵中。但输出看起来很奇怪，我的意思是，它不正确。我想在下面的代码中应该缺少或错误的东西。非常感谢任何一点帮助。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>
int main(int argc, char *argv[]){
int i=1,j, state=0, k, dist,x=0,y=0;

   int** myMat;
   char *city1, *city2, **matnames;
   FILE* p;
    city1 = (char*) malloc(sizeof(char));
    city2 = (char*) malloc(sizeof(char));
    matnames = (char**) malloc(sizeof(char*));
    myMat = (int**) malloc(sizeof(int*)*4);             
p = fopen(argv[1],"r");

/************************************************************/
    matnames[0] = (char*) malloc(sizeof(char));
    matnames[1] = (char*) malloc(sizeof(char));
    matnames[2] = (char*) malloc(sizeof(char));
    matnames[2] = NULL;
    fscanf(p, "%s %s %d", city1, city2, &dist);
        strcpy(matnames[0],city1);                  
        strcpy(matnames[1],city2);
/************************************************************/  
    for(i=0;i<3;i++){
        myMat[i] = (int*) malloc(sizeof(int));
    }
    myMat[1][2] = dist;         /* the first two distances placed at matnames */
    myMat[2][1] = dist;

/************************************************************/  
while( fscanf(p,"%s %s %d",city1,city2, &dist) != EOF){                 
        for(j=0; matnames[j]!=NULL; j++){                   
            if( strcmp(matnames[j], city1) != 0){
                 state++;
                }               
        }       
        if(state  == j){
            matnames = realloc(matnames, sizeof(char*)*(j+3));
            matnames[j] = (char*) malloc(sizeof(char));
            strcpy(matnames[j], city1);
            matnames[j+1] = (char*) malloc(sizeof(char));
            matnames[j+1] = NULL;   
            }
            state = 0;
        for(j=0; strcmp(matnames[j], city1) != 0;j++){ 
                x++;                   /* "x" finds the city1 indeks from matnames*/
        }

        for(k=0; matnames[k] != NULL;k++){                  
                if( strcmp(matnames[k], city2) != 0){
                    state++;
                }               
        }
        if(state == k){
            matnames = realloc(matnames, sizeof(char*)*(k+4));
            matnames[k] = (char*) malloc(sizeof(char));
            matnames[k+1] = (char*) malloc(sizeof(char));
            strcpy(matnames[k], city2); 
            matnames[k+1] = NULL;   
            }
        state = 0;
    /* till to here the names of cities are placed in matnames without repetion*/
        for(j=0; strcmp(matnames[j], city2) != 0;j++){ 
                y++;             /* "y" finds the city2 indeks from matnames*/
        }
        /****** the problem should be in this part */
        myMat = realloc(myMat,sizeof(int*)*(k+3));          
        for(i=2;i<k+2;i++){
            myMat[i] = (int*) malloc(sizeof(int));
        }
        myMat[x][y] = dist;
        myMat[y][x] = dist;
        x=0; y=0;
}   
return 0;
}

Answer 1

您将 1 个字符分配给 city1 和 city2(使用 sizeof(char) 进行 malloc)。除非您的城市都只有一个字符，否则 fscanf 将超出范围。

使用 city1 = (char*) malloc(1024) 重试，这样城市可以更长一些。

matnames 并不是很明显你想要它是什么，但你分配它 1 sizeof(pointer)，即 4 个字节。然后你做 matnames[0] = ..., matnames[1] = ...matnames[1] 已经溢出您分配的内存。所以你是在随机的地方写的。

C 语言对于内存分配非常宽容，但结果是完全不可预测的。确保您的 malloc 空间足够，并尽可能考虑其他语言。 :)