问写了个代码，目的是输入20个1-9的整数，然后求他们的平均值，中位数和众数？

代码不报错且不通过请大佬指点问题所在

#include<stdio.h>

#define size 20

double average(int a[size]);

double median( int a[size]);

int mode( int a[size]);

int main(void) {

int a[size];

printf("enter twenty integer from 1-9\n");

for(int i=0;i<size;i++){

scanf("%d ",&a[i]);

}

printf("average is %f",average(a[size]));

printf("median is %d",median(a[size]));

printf("mode is %d",mode(a[size]));

}

double average(int a[]){

double k=0;

for(int b=0;b<size;b++){

k+=a[b];

}

return k/size;

}

double median(int a[]){

int temp;

for(int x=0;x<size;x++){

for (int c=0;c<size;c++){

if(a[c]>a[c+1]){

temp=a[c];

a[c]=a[c+1];

a[c+1]=temp;

}

}

}

if (size%2==0){

return (a[size/2]+a[(size/2)+1])/2;

}

else{

return (int)a[size/2];

}

}

int mode(int a[]){

int count1=0;

int count2=0;

int count3=0;

int count4=0;

int count5=0;

int count6=0;

int count7=0;

int count8=0;

int count9=0;

for(int c=0;c<size;c++){

switch (a[c]){

case 1:++count1;break;

case 2:++count2;break;

case 3:++count3;break;

case 4:++count4;break;

case 5:++count5;break;

case 6:++count6;break;

case 7:++count7;break;

case 8:++count8;break;

case 9:++count9;break;

}

int d[]={count1,count2,count3,count4,count5,count6,count7,count8,count9};

for(int e=0;e<8;e++){

int f=d[0];

if (d[e]<d[e+1]){

f=d[e+1];

}

return d[e+1];

}

}

}