题目链接：uva 1549 - Lattice Point

题目大意：给定圆半径，以原点为圆心，求园内有多少个整数点。

解题思路：首先坐标轴将圆分成4份，所以只要单独考虑每一块的个数乘4再加1即可（原点）

#include 
   
     #include 
    
      #include 
     
       #include 
      
        using namespace std; const double pi = 4 * atan(1.0); typedef long long ll; ll solve (ll R) { ll ret = 0; ll r = R, M = R * R; for (ll i = 0; i <= R; i++) { while (r * r + i * i > M) r--; ret += r; } return 4 * ret + 1; } int main () { ll n; while (scanf("%lld", &n) == 1) { printf("%lld\n%lld\n", n, solve(n)); } return 0; }