初心者なりにがんばってみました
円周率を7行で
#include<stdio.h>
#include<time.h>
#include<stdlib.h>
int main(){int i,num=10000000;float a,b,answer,counter=0,r=30000;
srand((unsigned int)time(NULL));for(i=0;i<num;){if((a=rand())>r)continue;
if((b=rand())>r)continue;i++;if(((a-r/2)*(a-r/2)+(b-r/2)*(b-r/2))<(r*r/4))
counter++;}answer=(counter/num)*4;printf("%2.5f",answer);return 0;}