3.区间分组 区间问题

 

 

 用堆来维护每个组的max_r

#include <bits/stdc++.h>
using namespace std;
const int N = 100010;
struct Range {
    int l, r;
} range[N];
bool cmp(Range r1, Range r2) {
    return r1.l < r2.l;
}
int main() {
    int n;
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> range[i].l >> range[i].r;
    }
    sort(range, range + n, cmp);
    priority_queue<int, vector<int>, greater<int>> heap;
    for (int i = 0; i < n; i++) {
        Range t = range[i];
        if (!heap.size() || heap.top() >= t.l) { //需要开一个新的组
            heap.push(t.r); 
        } else { //放进这个组里，更新max_r
            heap.pop();
            heap.push(t.r);
        }
    }
    cout << heap.size() << endl;
    return 0;
}