poj 2018 Best Cow Fences

#include <stdio.h>#define MAX_N 100032double S[MAX_N], A[MAX_N];int N, F;int check(double val){    double cur, pre;    int i;    pre = S[F - 1] - val * (F - 1);    for (i = F; i <= N; i++) {        cur = S[i] - S[i - F] - val * F;        pre = pre + A[i] - val;        if (cur > pre) pre = cur;        if (pre > -1e-6) return 1;    }    return 0;}int main(){    int i;    double l, r, m;    scanf("%d%d", &N, &F);    l = 1e50;    r = 0;    A[0] = S[0] = 0;    for (i = 1; i <= N; i++) {        scanf("%lf", &A[i]);        if (A[i] > r) r = A[i];        if (A[i] < l) l = A[i];        S[i] = S[i - 1] + A[i];    }    while (r - l >= 1e-6) {        m = (l + r) / 2;        if (check(m)) l = m;        else r = m;    }    printf("%dn", (int)(r * 1000));    return 0;}