记录编号	602764	评测结果	AAAAA
题目名称	2698.环路运输	最终得分	100
用户昵称	LikableP	是否通过	通过
代码语言	C++	运行时间	0.177 s
提交时间	2025-07-05 16:41:19	内存使用	3.09 MiB

#include <cstdio>

template <typename T> T read();
template <typename T> void write(T, char);
template <typename T> T max(T, T);

const int MAXN = 2e6 + 10;

int n;
int a[MAXN << 1];
int que[MAXN << 1], front, tail;
int ans;

int main() {
  freopen("transportt.in", "r", stdin);
  freopen("transportt.out", "w", stdout);
  n = read<int>();
  for (int i = 1; i <= n; ++i) a[i] = a[i + n] = read<int>();

  que[front = tail = 1] = a[1];
  for (int i = 2; i <= n << 1; ++i) {
    while (front <= tail && i - que[front] > n / 2) ++front;
    ans = max(ans, a[i] + a[que[front]] + i - que[front]);
    while (front <= tail && a[i] - i >= a[que[tail]] - que[tail]) --tail;
    que[++tail] = i;
  }

  write(ans, '\n');
  return 0;
}

template <typename T> T max(T x, T y) {
  return x > y ? x : y;
}

#define isdigit(ch) ((ch) >= '0' && (ch) <= '9')
template <typename T> T read() {
  T res = 0, f = 1;
  char ch = getchar();
  for (; !isdigit(ch); ch = getchar())
    if (ch == '-') f = -1;
  for (; isdigit(ch); ch = getchar()) res = (res << 3) + (res << 1) + (ch ^ 48);
  return res * f;
}

template <typename T> void write(T x, char ed) {
  if (x < 0) x = -x, putchar('-');
  static int sta[sizeof(T) << 2], top = 0;
  do {
    sta[++top] = x % 10;
    x /= 10;
  } while (x);
  while (top) {
    putchar(sta[top--] ^ 48);
  }
  putchar(ed);
}