完善程序case1，功能234都无法运行出正确结果

#include <stdio.h>
#include <stdlib.h>
#define SIZE 30 //成绩数组总长度
#include <stdio.h>
#include <stdlib.h>
#define SIZE 30 //成绩数组总长度
#define SEGMENTSIZE 11 //分数段总共有0-10，总计11个段
#define FAILURE -1 //返回失败结果
#define SUCCESS 1 //返回成功结果
#define ASCEND 1 //升序
#define DECEND -1 //降序

int countStuNum(int array[], int length)
{
int i, stuNumber = 0;
for (i = 0; i < length; i++)
if (array[i] != -1)
stuNumber++; //因为数组的结尾是-1，统计非-1的个数
else break;
printf("stuNumber:%d\n", stuNumber);
return stuNumber;
}

int countMaxScore(int array[], int len)
{
int max = 0;
for(int i = 0; i < len; i++)
{
if(array[i] >= max)
max = array[i];
}

printf("MAX:%d\n", max);

return max;

}

int countMinScore(int array[], int len)
{
int min = 101;
for(int i = 0; i < len; i++)
{
if(array[i] <= min)
min = array[i];
}

printf("MIN:%d\n", min);

return min;

}

float countAverageScore(int array[], int len)
{
float ave, sum = 0;
for(int i = 0; i < len; i++)
{
sum += array[i];
}
ave = sum / len;
printf("AVE:%f\n", ave);

return ave;

}

int main()
{

//注：数组中有25个学生分数，其中最一个-1表示该元素之前的数组元素值为有效分数。
int score[SIZE] = { 78, 65, 23, 34, 56, 87, 90, 99, 45, 88, 54, 95, 63, 66, 89, 54, 64, 77, 63, 56, 5, 86, 97, 94, 30, -1 }; //给score[1]到score[25]赋初值。
int i;
int stuNumber, maxScore, minScore, searchArrayPosition;
int searchScore, appendScoreNum, insertScoreNum, result, arrayPossition;
int order;//排序方向
float averageScore, medianScore;
enum Status { GAMEOVER, CONTINUE };
int choiceNum;
enum Status gameStatus;

int len = 0;
do
{

    gameStatus = CONTINUE;
    printf("\n\t\t学  生  成  绩  管  理  系  统  1.3 \n\t\t\tDesigned by HuangX\n");
    printf("\n\t0.退出程序\t\t\t1.显示所有成绩\n\n");
    printf("\t2.统计最高分\t\t\t3.统计最低分\n\n");
    printf("\t4.统计平均分\t\t\n");
    printf("请选择功能:");

    scanf("%d", &choiceNum);
    fflush(stdin);//清除键盘缓冲区的数，否则当输入字符时会出现死循环

    switch (choiceNum)
    {
    case 0:
        gameStatus = GAMEOVER;
        return 1;
        break;
    case 1:
       
        break;
    case 2:
        countMaxScore( score,  len);
        break;
    case 3:
        countMinScore( score,  len);
        break;
    case 4:
        countAverageScore(score,  len);
        break;
    default:
        printf("输入错误，重新输入！\n");
        break;
    }
}
while(1);
return 0;

}

int score[] = { 78, 65, 23, 34, 56, 87, 90, 99, 45, 88, 54, 95, 63, 66, 89, 54, 64, 77, 63, 56, 5, 86, 97, 94, 30, -1 };
    int len= sizeof(score)/sizeof(int);

int len = 0
len都是0，当然算不出来
len = countStuNum(score , sizeof(score)/sizeof(int));