Poj--3277（线段树，离散化，线段更新、求和）

2014-10-01 16:53:27

思路：比较裸的线段树，考的是离散化和线段更新，即：叶子节点表示线段。

 1 /*************************************************************************
 2     > File Name: 3277.cpp
 3     > Author: Nature
 4     > Mail: 564374850@qq.com
 5     > Created Time: Wed 01 Oct 2014 03:46:19 PM CST
 6 ************************************************************************/
 7 
 8 #include <cstdio>
 9 #include <cstring>
10 #include <cstdlib>
11 #include <cmath>
12 #include <vector>
13 #include <queue>
14 #include <iostream>
15 #include <algorithm>
16 using namespace std;
17 #define lp (p << 1)
18 #define rp (p << 1|1)
19 #define getmid(l,r) (l + (r - l) / 2)
20 typedef long long ll;
21 const int INF = 1 << 29;
22 const int maxn = 80010;
23 
24 int N;
25 int val[maxn << 1];
26 
27 struct Building{
28     int a,b,h;
29     friend bool operator < (Building x,Building y){
30         return x.h < y.h;
31     }
32 }B[maxn];
33 
34 struct node{
35     int l,r;
36     int tl,tr,cover;
37     ll sum;
38 }t[maxn << 2];
39 
40 void Build_tree(int p,int l,int r){
41     t[p].l = l;
42     t[p].r = r;
43     t[p].tl = val[l];
44     t[p].tr = val[r];
45     t[p].cover = 0;
46     t[p].sum = 0;
47     if(l + 1 == r)
48         return;
49     int mid = getmid(l,r);
50     Build_tree(lp,l,mid);
51     Build_tree(rp,mid,r);
52 }
53 
54 void Push_down(int p){
55     int c = t[p].cover;
56     if(c){
57         t[lp].cover = t[rp].cover = c;
58         t[lp].sum = (ll)c * (t[lp].tr - t[lp].tl);
59         t[rp].sum = (ll)c * (t[rp].tr - t[rp].tl);
60         t[p].cover = 0;
61     }
62 }
63 
64 void Update(int a,int b,int c,int p,int l,int r){
65     if(a <= t[p].tl && t[p].tr <= b){
66         t[p].cover = c;
67         t[p].sum = (ll)c * (t[p].tr - t[p].tl);
68         return;
69     }
70     if(l + 1 == r) return;
71     Push_down(p);
72     int mid = getmid(l,r);
73     if(a <= t[lp].tr) Update(a,b,c,lp,l,mid);
74     if(b >= t[rp].tl) Update(a,b,c,rp,mid,r);
75     t[p].sum = t[lp].sum + t[rp].sum;
76 }
77 
78 int main(){
79     scanf("%d",&N);
80     int tot = 0;
81     for(int i = 1; i <= N; ++i){
82         scanf("%d%d%d",&B[i].a,&B[i].b,&B[i].h);
83         val[++tot] = B[i].a;
84         val[++tot] = B[i].b;
85     }
86     sort(val + 1,val + tot + 1);
87     Build_tree(1,1,2 * N);
88     sort(B + 1,B + N + 1);
89     for(int i = 1; i <= N; ++i){
90         Update(B[i].a,B[i].b,B[i].h,1,1,2 * N);
91     }
92     printf("%I64d\n",t[1].sum);
93     return 0;
94 }

 

posted @ 2014-10-01 16:54  Naturain  阅读(193)  评论(0)    收藏  举报