BZOJ 4800: [Ceoi2015]Ice Hockey World Championship
2017-10-25 17:03
369 查看
4800: [Ceoi2015]Ice Hockey World Championship
Time Limit: 10 Sec Memory Limit: 256 MBSubmit: 482 Solved: 257
[Submit][Status][Discuss]
Description
有n个物品,m块钱,给定每个物品的价格,求买物品的方案数。Input
第一行两个数n,m代表物品数量及钱数第二行n个数,代表每个物品的价格
n<=40,m<=10^18
Output
一行一个数表示购买的方案数(想怎么买就怎么买,当然不买也算一种)
Sample Input
5 1000100 1500 500 500 1000
Sample Output
8HINT
Source
题解:第一道双向搜索的题。。如果直接搜索的话,稳T,稳到不行,考虑双向搜索。先将物品折半,将前一半可以凑到的钱数存起来,后一半同理。
枚举前一半,在后一半里查找刚好不会超过钱数的个数,然后加起来。
自己随便口胡一下。。双向搜索大概就是一半枚举,一半查询?
#include<bits/stdc++.h> #define ll long long using namespace std; const int N = 40 + 5; const int M = 2000000 + 10; int n; ll m,a ,a1[M],a2[M]; int ed,cnt1=0,cnt2=0; void dfs(int x,int ed,ll sum,ll *ar,int &cnt){ if(sum>m) return ; if(x>ed){ ar[++cnt]=sum; return ; } dfs(x+1,ed,sum+a[x],ar,cnt); dfs(x+1,ed,sum,ar,cnt); } int main(){ // freopen("data.in","r",stdin); scanf("%d%lld",&n,&m); for(int i=1;i<=n;++i) scanf("%lld",&a[i]); ed=n>>1; dfs(1,ed,0,a1,cnt1); dfs(ed+1,n,0,a2,cnt2); sort(a1+1,a1+cnt1+1);sort(a2+1,a2+cnt2+1); ll ans=0; for(int i=1;i<=cnt1;++i){ if(a1[i]+a2[1]>m) break; ans+=upper_bound(a2+1,a2+cnt2+1,m-a1[i])-a2-1; } cout<<ans<<endl; return 0; }
相关文章推荐
- bzoj4800 [Ceoi2015]Ice Hockey World Championship
- BZOJ4800 [Ceoi2015]Ice Hockey World Championship
- BZOJ 4800: [Ceoi2015]Ice Hockey World Championship meet_in_the_middle
- [BZOJ4800][Ceoi2015][Meet In Middle]Ice Hockey World Championship
- bzoj 4800: [Ceoi2015]Ice Hockey World Championship meet in the middle
- 【BZOJ4800】[Ceoi2015]Ice Hockey World Championship Meet in the Middle
- BZOJ4800 [Ceoi2015]Ice Hockey World Championship
- 4800: [Ceoi2015]Ice Hockey World Championship
- bzoj4800: [Ceoi2015]Ice Hockey World Championship
- [BZOJ]4800: [Ceoi2015]Ice Hockey World Championship dfs+二分
- [bzoj4800][Ceoi2015]Ice Hockey World Championship
- BZOJ 4800 [Ceoi2015]Ice Hockey World Championship ……
- bzoj [4800] [Ceoi2015]Ice Hockey World Championship
- [BZOJ 4800][Ceoi2015]Ice Hockey World Championship:双向搜索
- BZOJ_4800_[Ceoi2015]Ice Hockey World Championship_双指针
- BZOJ 4800([Ceoi2015]Ice Hockey World Championship-meet in the middle)
- 【BZOJ】4800 [Ceoi2015]Ice Hockey World Championship 折半查找
- 【bzoj4800】[Ceoi2015]Ice Hockey World Championship 折半搜索
- bzoj4798[CEOI2015] Calvinball championship
- CEOI2015 Day1Task2 Calvinball championship