解决一个关于结构体的问题

#include <stdio.h>
struct student
{

 char num[10];

 char name[10];

 float score[4];
};
void main()
{
    struct student stu[5]={
    {"201060001","Zhao",85,86,88},
    {"201060002","Qian",87,88,89},
    {"201060003","Sun", 91,92,93},
    {"201060004","Li",  92,91,93},
    {"201060005","Wang",94,95,99}};
    int i;
    float max=0;
    printf("==========================================\n");
    printf("   Num       Name        Ave\n");
    for(i=0;i<5;i++)
    {stu[i].score[3]=(stu[i].score[0]+stu[i].score[1]+stu[i].score[2])/3.0;
    printf("%s    %s     %5.1f\n",
        stu[i].num,stu[i].name,stu[i].score[3]);}
    for(i=0;i<4;i++)
    {
     if(stu[i].score[3]<stu[i++].score[3])
         max=stu[i++].score;i++;
     printf("   Num   Name    score1  score2  score3  Ave\n");
     printf("%s    %s     %5.1f  %5.1f  %5.1f   %5.1f\n",
         stu[i].num,stu[i].name,stu[i].score[0],stu[i].score[1],stu[i].score[2],stu[i].score[3]);

    }
    printf("==========================================\n");
}