Submission #2551579

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Source Code Expand

#include <algorithm>
#include <cstring>
#include <cstdio>
struct point
{
	int x, y; 
	inline bool operator <(const point &a) const
	{
		return x < a.x; 
	}
} arr[300005], st1[300005], st2[300005]; 
int mx[1200005], lazy[1200005]; 
void modify(int u, int l, int r, int L, int R, int x)
{
	if (L <= l && r <= R)
	{
		mx[u] += x; 
		lazy[u] += x; 
		return; 
	}
	int m = l + r >> 1; 
	if (L <= m)
		modify(u << 1, l, m, L, R, x); 
	if (m < R)
		modify(u << 1 | 1, m + 1, r, L, R, x); 
	mx[u] = std::max(mx[u << 1], mx[u << 1 | 1]) + lazy[u]; 
}
int work(int w, int h, int n)
{
	memset(mx, -0x3f, sizeof(mx)); 
	memset(lazy, 0, sizeof(lazy)); 
	std::sort(arr, arr + n); 
	int tp1 = 0, tp2 = 0, ans = 0; 
	for (int i = 0; i < n - 1; i++)
	{
		int &tp = arr[i].y <= h / 2 ? tp1 : tp2, nxt = i - 1; 
		auto *st = arr[i].y <= h / 2 ? st1 : st2;
		while (tp && ((st[tp - 1].y < arr[i].y) ^ (arr[i].y > h / 2)))
		{
			modify(1, 0, n - 1, st[tp - 1].x, nxt, (st[tp - 1].y - arr[i].y) * (arr[i].y <= h / 2 ? 1 : -1)); 
			nxt = st[--tp].x - 1; 
		}
		if (nxt != i - 1)
			st[tp++] = {nxt + 1, arr[i].y}; 
		st1[tp1++] = {i, 0}; 
		st2[tp2++] = {i, h}; 
		modify(1, 0, n - 1, i, i, h - arr[i].x - mx[0]); 
		ans = std::max(ans, mx[1] + arr[i + 1].x); 
	}
	return ans; 
}
int main()
{
	// freopen("ARC063-F.in", "r", stdin); 
	int w, h, n; 
	scanf("%d%d%d", &w, &h, &n); 
	for (int i = 0; i < n; i++)
		scanf("%d%d", &arr[i].x, &arr[i].y); 
	arr[n++] = {0, 0}; 
	arr[n++] = {w, h}; 
	int ans = work(w, h, n); 
	for (int i = 0; i < n; i++)
		std::swap(arr[i].x, arr[i].y); 
	ans = std::max(ans, work(h, w, n)); 
	printf("%d\n", ans << 1);
	return 0; 
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:56:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d%d%d", &w, &h, &n); 
                             ^
./Main.cpp:58:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d%d", &arr[i].x, &arr[i].y); 
                                      ^

Judge Result