発展1
#include <stdio.h> int main() { double r; printf("Please input a positive real number as radius : "); scanf("%lf",&r); int R = (int) r + 1,i,j,ans = 0; for(i = -R;i <= R;i++){ for(j = -R;j <= R;j++){ double x = i,y = j; if(x*x + y*y <= r*r)ans++; } } printf("Number of points in the circle with r=%f : %d\n",r,ans); return 0; }