[JZOJ 5861] 失意

思路：
求交集最大老套路，排序之后用堆维护即可。

#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9+7;
const int maxn = 1000010;
inline int read() {
	int q=0,f=1;char ch = getchar();
	while(!isdigit(ch)){
		if(ch=='-')f=-1;ch=getchar();
	}
	while(isdigit(ch)){
		q=q*10+ch-'0';ch=getchar();
	}
	return q*f;
}
struct lne {
	int l,r,id;
	bool operator < (lne x) const{
		return r > x.r;
	}
}l[maxn];
int ans;
int n,m;
priority_queue<lne> q;
bitset<maxn>vis,p;
int siz;
inline bool cmp(lne a,lne b) {
	return (a.l == b.l) ? (a.r > b.r) : (a.l < b.l);
}
int main () {
	freopen("failure.in","r",stdin);
	freopen("failure.out","w",stdout);
	read();
	n = read(),m = read();
	for(int i = 1;i <= n; ++i) {
		l[i].l = read();
		l[i].r = read();
		l[i].id = i;
	}
	sort(l + 1,l + n + 1,cmp);
	for(int i = 1;i <= m; ++i) {
		q.push(l[i]);
		++siz;
		vis[l[i].id] = 1;
	}
	lne top = q.top();
	ans = max(top.r - l[m].l,0);
	p = vis;
	for(int i = m + 1;i <= n; ++i) {
		q.push(l[i]);
		++siz;
		vis[l[i].id] = 1;
		if(siz > m) {
			top = q.top();
			vis[top.id] = 0;
			q.pop();
			siz--;
		}
		if(siz == m) {
			top = q.top();
			int len = max(top.r - l[i].l,0);
			if(len >= ans) {
				ans = len;
				p = vis;
			}
		}
	}
	printf("%d\n",ans);
	for(int i = 1;i <= n; ++i) {
		if(p[i]) {
			printf("%d ",i);
		}
	}
	return 0;
}