Ural 1152. False mirrors (memory-based search-based DP)

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Each bullet destroys three neighboring balconies. (The n-day balcony is adjacent to the 1st) monsters that survive after the shooting all cause damage to the main character-so until all the monsters are eliminated, how to take a shot to minimize the damage.

Idea: pressure, data is not very big, it can be burst, or the DFS can go down and enumerate each State.

 1 //1152 2 #include <cstdio> 3 #include <cstring> 4 #include <iostream> 5 #define  oo 1 << 28 6 using namespace std ; 7  8 int a[110],dp[1 << 21] ; 9 bool vis[1 << 21] ;10 int n ;11 12 int DFS(int sta,int sum)13 {14     if(vis[sta]) return dp[sta] ;15     vis[sta] = true ;16     if(sta == 0) return dp[sta] = 0 ;17     int ans = oo ;18     for(int i = 0 ; i < n ; i++)19     {20         int newsta = sta ,newsum = sum ;21         for(int j = i-1 ; j <= i+1 ; j++)22         {23             int k = j ;24             if(j == -1) k = n-1 ;25             else if(j == n) k = 0 ;26             if(newsta & (1 << k))27             {28                 newsta -= (1 << k) ;29                 newsum -= a[k] ;30             }31         }32         if(newsta != sta)33             ans = min(ans,DFS(newsta,newsum)+newsum) ;34     }35     return dp[sta] = ans ;36 }37 int main()38 {39     while(~scanf("%d",&n))40     {41         int sum = 0 ;42         memset(a,0,sizeof(a)) ;43         memset(dp,63,sizeof(dp)) ;44         memset(vis,false,sizeof(vis)) ;45         for(int i = 0 ; i < n ; i++)46         {47             scanf("%d",&a[i]) ;48             sum += a[i] ;49         }50         dp[(1 << n)-1] = 0 ;51         printf("%d\n",DFS((1 << n)-1,sum)) ;52     }53     return 0 ;54 }

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Ural 1152. False mirrors (memory-based search-based DP)