[HIHO1079]离散化（线段树、染色）

题目链接：http://hihocoder.com/problemset/problem/1079

MD坑爹，线段查询的时候左闭右开。插完挨个点找一遍扔set里，注意没染色的情况。

#include <bits/stdc++.h>
using namespace std;

#define lson l, m, rt << 1
#define rson m + 1, r, rt << 1 | 1
const int maxn = 200100;
int sum[maxn<<2];

void pushDOWN(int rt) {
    if(sum[rt] != -1) {
        sum[rt<<1] = sum[rt<<1|1] = sum[rt];
        sum[rt] = -1;
    }
}

void update(int L, int R, int c, int l, int r, int rt) {
    if(L <= l && r <= R) {
        sum[rt] = c;
        return;
    }
    pushDOWN(rt);
    int m = (l + r) >> 1;
    if(L <= m) update(L, R, c, lson);
    if(R > m) update(L, R, c, rson);
}

int query(int p, int l, int r, int rt) {
    if(l == r) return sum[rt];
    pushDOWN(rt);
    int m = (l + r) >> 1;
    if(p <= m) return query(p, lson);
    else return query(p, rson);
}

int h[maxn], hcnt;
int n, m;
int lo[maxn], hi[maxn];

int id(int x) {
    return lower_bound(h, h+hcnt, x) - h + 1;
}

int main() {
    // freopen("in", "r", stdin);
    while(~scanf("%d%d",&n,&m)) {
        hcnt = 0;
        memset(sum, -1, sizeof(sum));
        for(int i = 0; i < n; i++) {
            scanf("%d%d",&lo[i], &hi[i]);
            h[hcnt++] = lo[i], h[hcnt++] = hi[i];
        }
        sort(h, h+hcnt); hcnt = unique(h, h+hcnt) - h;
        m = hcnt;
        for(int i = 0; i < n; i++) {
            update(id(lo[i]), id(hi[i])-1, i, 1, m, 1);
        }
        set<int> s;
        s.insert(-1);
        for(int i = 1; i <= m; i++) {
            s.insert(query(i, 1, m, 1));
            // printf("%d ", query(i, 1, m, 1));
        }
        // printf("\n");
        printf("%d\n", s.size()-1);
    }
    return 0;
}