c - Why my code is getting Runtime error? -

it took me 3 hrs logic solve question , code accordingly.

getting runtime error. can please me know mistake doing ? edit : running not printing anything.

http://ideone.com/2yls9j

#include <stdio.h> #include<math.h>  float distance(float n1,float m1,float n2,float m2){    float d=0;float sum=0;    d =sqrt(pow(m2-m1,2)+pow(n2-n1,2));    sum+=d;    printf("%.2f",sum);    return sum; }  int main(void) {    int t,n,i,j;float sum=0;    scanf("%d",&t);    while(t--){       scanf("%d",&n);       int r=0,s=0,a=0,b=0;       int x[n],y[n],p[n],q[n],min[n],max[n];       for(i=0;i<n;i++){          scanf("%d %d",&x[i],&y[i]);}        for(j=0;j<10001;j++){          for(i=0;i<n;i++){             if(j==x[i]){                p[r++]=x[i];q[s++]=y[i];             }          }}          for(i=0,j=i+1;i<n,j<n;i++,j++){             if(p[i]==p[j]){                if(q[i]>q[j]){min[a++]=p[i]; max[b++]=q[i];}                else{min[a++]=p[i]; max[b++]=q[j];}             }             else{min[a++]=p[i]; max[b++]=q[i];}          }        for(i=0;i<n;i++){          distance(min[i],max[i],min[i+1],max[i+1]);       }     } } 

this line:

        int x[n],y[n],p[n],q[n],min[n],max[n]; 

is not correct. in c/c++ cannot declare plain arrays of variable size (unlike, say, in basic). size of such array must known @ compile time.

possible solutions are:

1. use dynamic memory (malloc()/free())
2. use statically allocated arrays set maximum size (and either run risk of buffer overflow , memory corruption or make sure use no-more-than space have allocated for)
3. use std::vector<int>