c - 从 char 数组中解析 int

Question

我正在尝试读取边缘以空格分隔的图表。从 char* 缓冲区解析到整数时出现问题。

示例图:

1   2 
1   3
2   3
3   4
4   5
1   5
5   6 
1   6 

输出:

first edge: 1
second edge: 2
first edge: 0
second edge: 0
first edge: 1
second edge: 3
first edge: 0
second edge: 0
first edge: 2
second edge: 3
first edge: 0
second edge: 0
first edge: 3
second edge: 4
first edge: 0
second edge: 0
first edge: 4
second edge: 5
first edge: 0
second edge: 0
first edge: 1
second edge: 5
first edge: 0
second edge: 0
first edge: 5
second edge: 6
first edge: 0
second edge: 0
first edge: 0
second edge: 0
first edge: 1
second edge: 6
first edge: 0
second edge: 0
first edge: 0
second edge: 0

显然所有这些零不应该在那里。

代码:

#include <stdio.h>
#include <math.h>
#include <ctype.h>

int main(int argc, char* argv[]){   

    FILE *fin; 
    fin = fopen(argv[1], "r");
    int n_e = 0;
    char* buffer = (char*)malloc(2048);
    char* n1 = (char*)malloc(256); 
    char* n2 = (char*)malloc(256);
    int v_1 = 0; 
    int v_2 = 0;
    int flag = 0; 

    while(!feof(fin)){
        int bytes_read = fread(buffer, 1, 2048, fin);
        for(int i = 0; i < bytes_read; i++){
            if(isdigit(buffer[i])){
                if(flag == 0){ 
                    n1[v_1++] = buffer[i];
                }
                else 
                    n2[v_2++] = buffer[i]; 
            }
            else if(buffer[i] == ' ')
                flag = 1; 
            else{ //end of the line??
                n_e++;
                flag = 0; 
                n1[v_1++] = '\0';
                n2[v_2++] = '\0';
                int first = atoi(n1);
                int second = atoi(n2);
                printf("first edge: %d\n", first);
                printf("second edge: %d\n", second);
                v_1 = 0;
                v_2 = 0;
            }
        }
    }

return 0;
}

Answer 1

您可以在一行中实现您想要的核心:fscanf 行。剩下的部分专门用于框架和错误检查——这是任何程序的重要组成部分。将图形边缘作为文本文件给出:

#include <stdio.h>

int main(int argc, char *argv[]) {
    FILE *fin; 
    int first, second;
    if(argc < 2) {                                      // check # arguments
        return 0;                                       // or other action
    }
    fin = fopen(argv[1], "rt");
    if(fin == NULL) {                                   // check the file opened
        return 0;                                       // or other action
    }
    while(fscanf(fin, "%d%d", &first, &second) == 2) {  // check the number of items read
        printf("first edge: %d, second edge: %d\n", first, second);
    }
    fclose(fin);
    return 0;
}

程序输出:

first edge: 1, second edge: 2
first edge: 1, second edge: 3
first edge: 2, second edge: 3
first edge: 3, second edge: 4
first edge: 4, second edge: 5
first edge: 1, second edge: 5
first edge: 5, second edge: 6
first edge: 1, second edge: 6

另请注意，feof 的使用方式与您的方式不同，如上面所评论的。