hihoCoder 1227 The Cats' Feeding Spots(水)

题目链接：hihoCoder 1227 The Cats’ Feeding Spots

代码

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

using namespace std;
const int maxn = 105;
const int inf = 0x3f3f3f3f;

int M, N;
double X[maxn], Y[maxn], D[maxn][maxn];

double dis(double x, double y) {
    return sqrt(x*x + y*y);
}

int main () {
    int cas;
    scanf("%d", &cas);
    for (int kcas = 1; kcas <= cas; kcas++) {
        scanf("%d%d", &M, &N);
        for (int i = 1; i <= M; i++) {
            scanf("%lf%lf", &X[i], &Y[i]);
            for (int j = 1; j <= i; j++)
                D[i][j] = D[j][i] = dis(X[i]-X[j], Y[i]-Y[j]);
        }

        int ans = inf;
        for (int i = 1; i <= M; i++) {
            sort(D[i] + 1, D[i] + 1 + M);
            int r = ceil(D[i][N]);
            for (int k = 0; k < 2; k++) {
                int c = 0, flag = 1;
                for (int j = 1; j <= M && flag; j++) {
                    if (fabs(D[i][j] - r) < 1e-6) flag = 0;
                    if (D[i][j] < r) c++;
                }

                if (flag && c == N) {
                    ans = min(ans, r);
                }
                r++;
            }
        }
        if (ans == inf) ans = -1;
        printf("%d\n", ans);
    }
    return 0;
}