C语言结构体数组及结构体指针例题

#include<stdio.h>
struct Student{
    int num;
    char name[20];
    float score;
};
int main(){
    struct Student a[3]={{1,"zhangsan",90},
    {2,"list",80},
    {3,"wangwu",100
    }};
    struct Student max=a[0];
    int i;
    for(i=0;i<=2;i++){
        if(max.score<a[i].score)max=a[i];
    }
    printf("%d %s %f\n",max.num,max.name,max.score);
    return 0;
}

#include<stdio.h>
struct Student{
    int num;
    char name[20];
    float score;
};
int main(){
    struct Student a[5]={{1,"zhangsan",90},
    {2,"list",80},
    {3,"wangwu",100
    },{3,"wangwu",50
    },{3,"wangwu",72
    }};
    struct Student temp;
    int j;
    for(j=1;j<=4;j++){
        int i;
        for(i=0;i<=3;i++){
            if(a[i].score<a[i+1].score){
                temp=a[i];
                a[i]=a[i+1];
                a[i+1]=temp;
            }
        } 
    }
    int i;
    for(i=0;i<=4;i++){
        printf("%d %s %f\n",a[i].name,a[i].name,a[i].score);
    }
    return 0;
}

#include<stdio.h>
#include<string.h>
struct Student{
    int num;
    char name[20];
    float score[3];
    float avg;
};
int main(){
    struct Student stu[3];
    stu[0].num=1;strcpy(stu[0].name,"zhangsan");
    stu[0].score[0]=90;stu[0].score[1]=80;
    stu[0].score[2]=75;
    stu[0].avg=stu[0].score[0]/3+
    stu[0].score[1]/3+stu[0].score[2]/3;
    stu[1].num=2;strcpy(stu[1].name,"list");
    stu[1].score[0]=98;stu[1].score[1]=60;
    stu[1].score[2]=72;
    stu[1].avg=stu[1].score[0]/3+
    stu[1].score[1]/3+stu[1].score[2]/3;
    stu[2].num=3;strcpy(stu[2].name,"wangwu");
    stu[2].score[0]=70;stu[2].score[1]-90;
    stu[2].score[2]=86;
    stu[2].avg=stu[2].score[2]/3;
    struct Student max=stu[0];
    int i;
    for(i=0;i<=2;i++){
        if(max.avg<stu[i].avg)max=stu[i]; 
    }
    printf("%d %s %f %f %f %f",max.num,max.name,max.score[0],max.score[1],max.score[2],max.avg);
    return 0;
}