SGU - 133 - Border （簡單統計）

SGU - 133 - Border （簡單統計）

133. Border

time limit per test: 0.25 sec.
memory limit per test: 4096 KB

Along the border between states A and B there are N defence outposts. For every outpost k, the interval [A_k,B_k] which is guarded by it is known. Because of financial reasons, the president of country A decided that some of the outposts should be abandoned. In fact, all the redundant outposts will be abandoned. An outpost i is redundant if there exists some outpost j such that A_ji and B_ij. Your task is to find the number of redundant outposts.

Input

The first line of the input will contain the integer number N (1<=N<=16 000). N lines will follow, each of them containing 2 integers: A_k and B_k (0<= A_k < B_k <= 2 000 000 000), separated by blanks. All the numbers A_k will be different. All the numbers B_k will be different.

Output

You should print the number of redundant outposts.

Sample Input

5
0 10
2 9
3 8
1 15
6 11

Sample Output

3

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Author : Mugurel Ionut Andreica Resource : SSU::Online Contester Fall Contest #2 Date : Fall 2002

思路：將整數對按照第一個值升序排列，然後往後遍歷，每次的第二個值如果比之前的第二個值中的最大值小，則ans++，注意不要加EOF，會PE

AC代碼：

#include 
#include 
#include 
#include 
using namespace std;

struct node {
	int x, y;
}a[16005];

int N;

bool cmp(node a, node b) {
	return a.x < b.x;
}

int main() {
	scanf("%d", &N);
	for(int i = 0; i < N; i++) {
	scanf("%d %d", &a[i].x, &a[i].y);
	}
	sort(a, a + N, cmp);
	
	int ans = 0;
	int MAX = a[0].y;
	for(int i = 1; i < N; i++) {
		if(a[i].y < MAX) ans ++;
		else MAX = a[i].y;
	}
	
	printf("%d\n", ans);
	return 0;
}