Codeforces Round #512(Technocup 2019 Elimination Round 1) B. Vasya and Cornfield (Codeforces 1030B)

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题目：Vasya and Cornfield

题意：给出两个整数n，d，代表有一个在第一象限的矩形，坐标是(0,d) (d,0) (n,n-d) (n-d,n)，再给出一些点的坐标，求出这些点是否在矩形中。

思路：分类讨论下。

代码：

#include<bits/stdc++.h>
using namespace std;

#define ll long long
#define inf (1<<30)
#define read(x) scanf("%d",&x)
#define maxn 100

int n,d;
int m;
int a[maxn+5];

void readin() {
	read(n);read(d);read(m);
	if(d<=n-d) for(int i=1;i<=m;i++) {
		int x,y;
		read(x);read(y);
		if(x<=d&&y<=d) {
			if(x+y>=d) printf("YES\n");
			else printf("NO\n");
		} else if(x>=n-d&&y>=n-d) {
			if(x+y<=2*n-d) printf("YES\n");
			else printf("NO\n");
		} else {
			if(y-x>=-d&&y-x<=d) printf("YES\n");
			else printf("NO\n");
		}
	}
	else for(int i=1;i<=m;i++) {
		int x,y;
		read(x);read(y);
		if(x<=n-d&&y>=d) {
			if(y-x<=d) printf("YES\n");
			else printf("NO\n");
		} else if(x>=d&&y<=n-d) {
			if(x-y<=d) printf("YES\n");
			else printf("NO\n");
		} else {
			if((x+y<d)||(x+y>n*2-d)) printf("NO\n");
			else printf("YES\n");
		}
	}
}

int main() {
	readin();
	return 0;
}