Codeforces 527D Clique Problem

题意：给你一个xi,wi的点集合，问你其中最大的子集满足|xi - xj| >= wi + wj 的大小是多少。

解题思路：dp+离散化+树状数组。把它看成是一条边[xi-wi,xi+wi] 去覆盖区域就行了

解题代码：

  1 // File Name: d.cpp
  2 // Author: darkdream
  3 // Created Time: 2015年03月18日 星期三 15时28分50秒
  4 
  5 #include<vector>
  6 #include<list>
  7 #include<map>
  8 #include<set>
  9 #include<deque>
 10 #include<stack>
 11 #include<bitset>
 12 #include<algorithm>
 13 #include<functional>
 14 #include<numeric>
 15 #include<utility>
 16 #include<sstream>
 17 #include<iostream>
 18 #include<iomanip>
 19 #include<cstdio>
 20 #include<cmath>
 21 #include<cstdlib>
 22 #include<cstring>
 23 #include<ctime>
 24 #define LL long long
 25 
 26 using namespace std;
 27 #define maxn 700000
 28 int lowbit(int x)
 29 {
 30    return x &(-x);
 31 }
 32 int tree[maxn];
 33 int getsum(int x)
 34 {
 35     int sum = 0;
 36     while(x >= 1)
 37     {
 38         sum = max(tree[x],sum);
 39         x -= lowbit(x);
 40     }
 41     return sum; 
 42 }
 43 int n,m,tt; 
 44 void update(int k ,int v)
 45 {
 46     while(k <= tt) 
 47     {
 48       tree[k] =  max(tree[k],v); 
 49       k += lowbit(k);
 50     }
 51 }
 52 struct node{
 53     int x ,l , r; 
 54 }qu[maxn];
 55 int cmp(int x, int y)
 56 {
 57   return x < y ; 
 58 }
 59 int nodecmp(node x, node y)
 60 {
 61     return x.x < y.x; 
 62 }
 63 map<int ,int > mp;
 64 int ch[maxn];
 65 int main(){
 66      m = 0 ; 
 67      scanf("%d",&n);
 68      int tm;
 69      for(int i = 1;i <= n;i ++)
 70      {
 71         scanf("%d %d",&qu[i].x,&tm);
 72         qu[i].l = qu[i].x - tm;
 73         qu[i].r = qu[i].x + tm;
 74         ch[m+1] = qu[i].l; 
 75         ch[m+2] = qu[i].r;
 76         m += 2; 
 77      }
 78      sort(qu+1,qu+1+n,nodecmp);
 79      sort(ch+1,ch+1+m,cmp);
 80      ch[0] = -1e9- 1000;
 81      tt = 0 ; 
 82      for(int i =1 ;i <= m;i ++)
 83      {
 84          if(ch[i] != ch[i-1]) 
 85          {
 86            tt ++ ;
 87            mp[ch[i]]  = tt; 
 88          }
 89      }
 90      int ans = 0 ;
 91      for(int i = 1;i <= n;i ++)
 92      {
 93         int l = mp[qu[i].l];
 94         ans = getsum(l); 
 95         //printf("%d %d %I64d\n",l,mp[qu[i].r],getsum(l));
 96         update(mp[qu[i].r],ans +1);
 97      }
 98      ans = getsum(tt);
 99      printf("%d\n",ans); 
100 return 0;
101 }

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posted on 2015-03-18 18:46 dark_dream 阅读(250) 评论(0) 编辑收藏举报