C语言程序问题，向大家请教

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int a[2][3];
    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 3; j++)
            scanf("%d", &a[i][j]);
    }

    int max = a[0][0];
    int col=0;
    for (int j = 0; j < 3; j++)
    {
        if (abs(a[0][j]) > abs(max))
        {
            max=a[0][j];
            col=j;
        }
    }
    printf("MAX:%d\n",max);

    int tmp;
    for (int i = 0; i < 2; i++)
    {
        tmp=a[i][0];
        a[i][0]=a[i][col];
        a[i][col]=tmp;        
    }

    FILE *fp=fopen("test.txt","w+");
    if(fp==NULL)
    {
        printf("打开文件错误！\n");
        exit(-1);
    }
    for (int i = 0; i < 2; i++)
    {
        for (int j = 0; j < 3; j++)
        {
            printf("%d ",a[i][j]);
            fprintf(fp,"%d ",a[i][j]);
        }

        printf("\n");
        fprintf(fp,"\n");
    }

    fclose(fp);

    return 0;
}