1469C Building a Fence

题目

思路：每一次求取一个范围，然后判断之后的小方格是否满足范围。对于最后和第一个方格已经取定，需要特殊判断，细节见代码。

Code:

#include
#include
#include
#include
#include
#include
#define pii pair
#define FAST ios::sync_with_stdio(false),cin.tie(0),cout.tie(0)
using namespace std;
typedef long long ll;
const int Max = 1e6 + 5;
int Mod = 1e9 + 7;
int h[Max];
int main()
{
     
	int t;cin >> t;
	while (t--)
	{
     
		int n, k;cin >> n >> k;
		for (int i = 1;i <= n;i++)cin >> h[i];
		int l = h[1], r = h[1];
		int f = 1;
		for (int i = 2;i <= n-1;i++)
		{
     
			if (h[i] >= h[i - 1])
			{
     
				if (h[i] >= r + k) {
      f = 0;break; }
				l = h[i], r = min(h[i] + k-1, r + k - 1);
			}
			else
			{
     
				if (h[i] + k+k-1 <= l) {
      f = 0;break; }
				r = h[i] + k - 1, l = max(h[i], l - k + 1);
			}
		}
		if (h[n] + k <= l || h[n] >= r + k)f = 0;
		if (f)cout << "YES" << endl;
		else cout << "NO" << endl;

	}
}