Codeforces 460C Present(二分)

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

using namespace std;
const int maxn = 1e5+5;
const int inf = 1e9+maxn;

int N, M, W, arr[maxn], v[maxn];

bool judge (int k) {
int ti = M, n = 0;
memset(v, 0, sizeof(v));

for (int i = 1; i <= N; i++) {
n += v[i];
int tmp = max(k - arr[i] - n, 0);

ti -= tmp;
if (ti < 0)
return false;

if (i + 1 <= N)
v[i+1] += tmp;
if (i + W <= N)
v[i+W] -= tmp;
}
return true;
}

int bsearch (int l, int r) {
for (int i = 0; i < 80; i++) {
int mid = (r + l) / 2;
if (judge(mid))
l = mid;
else
r = mid;
}
return l;
}

int main () {
scanf("%d%d%d", &N, &M, &W);
for (int i = 1; i <= N; i++)
scanf("%d", &arr[i]);
printf("%d\n", bsearch(1, inf));
return 0;
}