AcWing 906. 区间分组

//1.将所有区间按左端点从小到大排序
//2.从前往后处理每个区间，判断能否将其放到某个现有的组中
//判断某一组的最后一个区间的右端点是否小于该区间的左端点
//如果大于或等于，就开新组，如果小于，就放到组里去，并更新最后一个区间的右端点
#include <iostream>
#include <algorithm>
#include <queue>
using namespace std;
const int N = 100010;
int n;
struct Range {
    int l, r;
    bool operator< (const Range &W)const {
        return l < W.l;
    }
} range[N];
int main() {
    scanf("%d", &n);
    for (int i = 0; i < n; i ++ ) {
        int l, r;
        scanf("%d%d", &l, &r);
        range[i] = {l, r};
    }
    sort(range, range + n);
    priority_queue<int, vector<int>, greater<int>> heap;//维护所有组的右端点的最大值
    for (int i = 0; i < n; i ++ ) {
        auto r = range[i];
        if (heap.empty() || heap.top() >= r.l)
            heap.push(r.r);
        else {
            heap.pop();
            heap.push(r.r);
        }
    }
    printf("%d\n", heap.size());
    return 0;
}