改了一点,AC了
首先这个题数据范围不应该开到1e6吗,你怎么是6e5;
其次,输入的时候数组下标从1开始的,那么排序就应该sort(a+1,a+1+n);直接sort(a,a+n)是下标从0到n-1排序
```cpp
#include<bits/stdc++.h>
using namespace std;
typedef pair<int, int> pi;
const int N = 1e6 + 5;
pi a[N];
int n;
int main() {
cin >> n;
for (int i = 1; i <= n; i++) cin >> a[i].second >> a[i].first;
sort(a + 1, a + 1 + n);
int ans = 0, last = 0;
for (int i = 1; i <= n; i++) {
if (a[i].second >= last) {
last = a[i].first;
ans++;
}
}
cout << ans;
return 0;
}
```
by Doppler @ 2024-01-25 11:13:59