51Nod－1098－最小方差

ACM模版

描述

题解

排序后枚举即可。注意数据溢出问题，还有INF值的设定，因为一开始设置成了0x3f3f3f3f导致无法保证初始化的值足够大，后增大了INF方AC！

代码

#include <iostream>
#include <algorithm>
#include <cstdio>

using namespace std;

const int MAXN = 1e4 + 10;
const long long INF = 0x3f3f3f3f3f3f3f3f;

int num[MAXN];
long long sum[MAXN] = {
  0};

int main(int argc, const char * argv[])
{
    freopen("/Users/zyj/Desktop/input.txt", "r", stdin);

    int M, N;
    cin >> M >> N;

    for (int i = 1; i <= M; i++)
    {
        scanf("%d", num + i);
    }
    sort(num + 1, num + M + 1);
    for (int i = 1; i <= M; i++)
    {
        sum[i] = sum[i - 1] + num[i];
    }

    double SSN = INF;
    for (int i = 1; i <= M - N + 1; i++)
    {
        double k = (sum[i + N - 1] - sum[i - 1]) * 1.0 / N;
        long double S = 0;
        for (int j = 0; j < N; j++)
        {
            S += (num[i + j] - k) * (num[i + j] - k);
        }
        SSN = SSN > S ? S : SSN;
    }

    std::cout << (long long)SSN << '\n';
    return 0;
}