[HIHO1079]离散化（线段树、染色）

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 
 4 #define lson l, m, rt << 1
 5 #define rson m + 1, r, rt << 1 | 1
 6 const int maxn = 200100;
 7 int sum[maxn<<2];
 8 
 9 void pushDOWN(int rt) {
10     if(sum[rt] != -1) {
11         sum[rt<<1] = sum[rt<<1|1] = sum[rt];
12         sum[rt] = -1;
13     }
14 }
15 
16 void update(int L, int R, int c, int l, int r, int rt) {
17     if(L <= l && r <= R) {
18         sum[rt] = c;
19         return;
20     }
21     pushDOWN(rt);
22     int m = (l + r) >> 1;
23     if(L <= m) update(L, R, c, lson);
24     if(R > m) update(L, R, c, rson);
25 }
26 
27 int query(int p, int l, int r, int rt) {
28     if(l == r) return sum[rt];
29     pushDOWN(rt);
30     int m = (l + r) >> 1;
31     if(p <= m) return query(p, lson);
32     else return query(p, rson);
33 }
34 
35 int h[maxn], hcnt;
36 int n, m;
37 int lo[maxn], hi[maxn];
38 
39 int id(int x) {
40     return lower_bound(h, h+hcnt, x) - h + 1;
41 }
42 
43 int main() {
44     // freopen("in", "r", stdin);
45     while(~scanf("%d%d",&n,&m)) {
46         hcnt = 0;
47         memset(sum, -1, sizeof(sum));
48         for(int i = 0; i < n; i++) {
49             scanf("%d%d",&lo[i], &hi[i]);
50             h[hcnt++] = lo[i], h[hcnt++] = hi[i];
51         }
52         sort(h, h+hcnt); hcnt = unique(h, h+hcnt) - h;
53         m = hcnt;
54         for(int i = 0; i < n; i++) {
55             update(id(lo[i]), id(hi[i])-1, i, 1, m, 1);
56         }
57         set<int> s;
58         s.insert(-1);
59         for(int i = 1; i <= m; i++) {
60             s.insert(query(i, 1, m, 1));
61             // printf("%d ", query(i, 1, m, 1));
62         }
63         // printf("\n");
64         printf("%d\n", s.size()-1);
65     }
66     return 0;
67 }