0
1
mirror of https://git.sb/baoshuo/OI-codes.git synced 2024-12-25 18:52:06 +00:00
OI-codes/S2OJ/1858/1858.cpp

116 lines
2.0 KiB
C++
Raw Normal View History

#include <iostream>
using std::cin;
using std::cout;
const char endl = '\n';
const int N = 1e5 + 5;
int n, k, t;
long long x[N], a[N];
bool check(int v) {
for (int i = 1; i <= n; i++) {
a[i] = x[i] - 2ll * v * t * i;
}
if (a[n] > a[1]) {
return false;
}
int l = k, r = k;
for (int i = k - 1; i >= 1; i--) {
if (a[l] - a[i] <= 0) l = i;
}
for (int i = k + 1; i <= n; i++) {
if (a[i] - a[r] <= 0) r = i;
}
int l1 = k, r1 = k;
while (l < l1 || r1 < r) {
int nl = l1, nr = r1;
bool flag = false;
while (l < nl && a[r1] - a[nl - 1] <= 0) {
if (a[l1] - a[--nl] <= 0) break;
}
if (nl < l1 && a[l1] - a[nl] <= 0) {
l1 = nl;
flag = true;
}
while (nr < r && a[nr + 1] - a[l1] <= 0) {
if (a[++nr] - a[r1] <= 0) break;
}
if (r1 < nr && a[nr] - a[r1] <= 0) {
r1 = nr;
flag = true;
}
if (!flag) return false;
}
int l2 = 1, r2 = n;
while (l2 < l || r < r2) {
int nl = l2, nr = r2;
bool flag = false;
while (nl < l && a[r2] - a[nl + 1] <= 0) {
if (a[++nl] - a[l2] >= 0) break;
}
if (l2 < nl && a[nl] - a[l2] >= 0) {
l2 = nl;
flag = true;
}
while (r < nr && a[nr - 1] - a[l2] <= 0) {
if (a[r2] - a[--nr] >= 0) break;
}
if (nr < r2 && a[r2] - a[nr] >= 0) {
r2 = nr;
flag = true;
}
if (!flag) return false;
}
return true;
}
int main() {
std::ios::sync_with_stdio(false);
cin.tie(nullptr);
cin >> n >> k >> t;
for (int i = 1; i <= n; i++) {
cin >> x[i];
}
int l = 0, r = 1e9,
res = 0;
while (l <= r) {
int mid = (l + r) >> 1;
if (check(mid)) {
r = mid - 1;
res = mid;
} else {
l = mid + 1;
}
}
cout << res << endl;
return 0;
}