uva 1549 - Lattice Point(暴力)

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題目連結：uva 1549 - Lattice Point

題目大意：給定圓半徑，以原點為圓心，求園內有多少個整數點。

解題思路：首先座標軸將圓分成4份，所以只要單獨考慮每一塊的個數乘4再加1即可（原點）

#include <cstdio>#include <cstring>#include <cmath>#include <algorithm>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;}