Mayor's posters https://vjudge.net/problem/POJ-2528#author=szdytom

线段树 + 离散化

讲解：https://blog.csdn.net/qq_35802619/article/details/98326267

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
using namespace std;
#define sc(n) scanf("%c",&n)
#define sd(n) scanf("%d",&n)
#define pd(n) printf("%d\n", (n))
#define sdd(n,m) scanf("%d %d",&n,&m)
#define pdd(n,m) printf("%d %d\n",n, m)
#define ms(a,b) memset(a,b,sizeof(a))
#define all(c) c.begin(),c.end()typedef long long ll;
const int maxn = 2e5 + 5;//数组注意别开小了struct node {int l, r, gg;
}tr[maxn << 2 + 5];
int lg[maxn], rg[maxn];
int lisan[maxn];
int cnt, ans;
bool book[maxn];void build(int p, int l, int r) {tr[p].l = l, tr[p].r = r;if (l == r) {tr[p].gg = 0; return;}int m = (l + r) >> 1;build(p << 1, l, m);build(p << 1 | 1, m + 1, r);tr[p].gg = 0;
}void spread(int q) {if (tr[q].gg == 0) return;tr[q << 1].gg = tr[q].gg;tr[q << 1 | 1].gg = tr[q].gg;tr[q].gg = 0;
}void update(int q, int l, int r, int v) {if (l <= tr[q].l && r >= tr[q].r) {tr[q].gg = v; return;}spread(q);int m = (tr[q].l + tr[q].r) >> 1;if (l <= m) update(q << 1, l, r, v);if (r > m) update(q << 1 | 1, l, r, v);
}void ask(int q, int l, int r)
{if (tr[q].gg && !book[tr[q].gg]){ans++;book[tr[q].gg] = 1;return;}if (l == r) return;spread(q);int mid = (l + r) >> 1;ask(q << 1, l, mid);ask(q << 1 | 1, mid + 1, r);
}int main() {//freopen("in.txt", "r", stdin);//ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);int t, n; sd(t);while (t--) {cnt = 0; ms(book, false); sd(n);for (int i = 0; i < n; ++i) {sdd(lg[i], rg[i]);lisan[cnt++] = lg[i];lisan[cnt++] = rg[i];}//离散化sort(lisan, lisan + cnt);int m = unique(lisan, lisan + cnt) - lisan;int t0 = m;for (int i = 1; i <= m; ++i)if (lisan[i] - lisan[i - 1] > 1)lisan[t0++] = lisan[i - 1] + 1;sort(lisan, lisan + t0);build(1, 1, t0);for (int i = 0; i < n; ++i) {int x = lower_bound(lisan, lisan + t0, lg[i]) - lisan + 1;int y = lower_bound(lisan, lisan + t0, rg[i]) - lisan + 1;//  cout <<x << " " << y << endl;update(1, x, y, i + 1);}ans = 0;ask(1, 1, t0);printf("%d\n", ans);}return 0;
}