ural 1152 搜索或状压

来源：互联网发布：garch模型 python 编辑：程序博客网时间：2024/05/05 06:42

n个阳台，每个阳台上有怪物，第一个阳台跟最后一个相邻，每次攻击其中一个阳台，那么相邻的两个也会被破坏掉，但是你攻击一次，剩下的没有被消灭的怪兽就会攻击你，问消灭所有怪兽所受伤害值最少是多少

#include <bits/stdc++.h>#include<cmath>#include<cstdlib>#define INF 0x3f3f3f3fusing namespace std;int ans;int n;int a[25];int sum=0;int vis[1000];int Mi=INF;void DFS(int sum,int mi){    if(mi>=Mi)      ///剪枝        return ;    if(sum==0)    {        Mi=min(Mi,mi);        return;    }    for(int i=0; i<n; i++)    {        if(!vis[i])        {            int t1=(i+n-1)%n;            int t2=(i+1)%n;            vis[i]=1;            if(!vis[t1]&&!vis[t2])            {                vis[t1]=vis[t2]=1;                sum=sum-a[t1]-a[t2]-a[i];                mi+=sum;                DFS(sum,mi);                vis[t1]=vis[t2]=0;                mi-=sum;                sum=sum+a[t1]+a[t2]+a[i];            }            else if(!vis[t1])            {                sum=sum-a[t1]-a[i];                mi+=sum;                vis[t1]=1;                DFS(sum,mi);                vis[t1]=0;                mi-=sum;                sum=sum+a[t1]+a[i];            }            else if(!vis[t2])            {                sum=sum-a[t2]-a[i];                mi+=sum;                vis[t2]=1;                DFS(sum,mi);                vis[t2]=0;                mi-=sum;                sum=sum+a[t2]+a[i];            }            else    ///忘记自己本身也要相加了            {                sum=sum-a[i];                mi+=sum;                DFS(sum,mi);                mi-=sum;                sum=sum+a[i];            }            vis[i]=0;        }    }}int main(){    while(~scanf("%d",&n))    {        Mi=INF;        memset(vis,0,sizeof(vis));        sum=0;        for(int i=0; i<n; i++)        {            scanf("%d",&a[i]);            sum+=a[i];        }        DFS(sum,0);        printf("%d\n",Mi);    }    return 0;}

记忆化搜索写法

#include<cstdio>#include<cstdlib>#include<cstring>#include<algorithm>#include<iostream> using namespace std;int a[25], f[(1<<21)+10];bool vis[(1<<21)+10];int n;int dfs(int x, int s){if (vis[x]) return f[x];vis[x]=true;if (x==0) return f[x]=0;int res=2100000000;for (int i=1; i<=n; i++){int newx=x, news=s;for (int j=i-1; j<=i+1; j++){int k=j;if (j==0) k=n; else if (j==n+1) k=1;if (newx&(1<<(k-1))){news-=a[k];newx-=(1<<(k-1));}}if (newx!=x)res=min(res, dfs(newx, news)+news);}return f[x]=res;} int main(){int s=0;scanf("%d", &n);for (int i=1; i<=n; i++) {scanf("%d", &a[i]);s+=a[i];}memset(f, 63, sizeof(f));memset(vis, 0, sizeof(vis));f[(1<<n)-1]=0;printf("%d", dfs((1<<n)-1, s));}//hzj

1 0