10400 - Game Show Math

用状态方程来剪枝的一种方式

# include<stdio.h># include<stdlib.h># include<string.h>int dfs(long ans,int cur);int range(long a);long number[105],que;int n,vis[64010][110];char record[105];int main(){int test;scanf("%d",&test);record[0]=0;while(test--){  scanf("%d",&n);  for(int i=0;i<n;i++)scanf("%ld",&number[i]);  scanf("%ld",&que);  memset(vis,0,sizeof(vis));  if(dfs(number[0],1))  {  printf("%ld",number[0]);  for(int i=1;i<n;i++)  {  printf("%c%ld",record[i],number[i]);  }  printf("=%ld\n",que);  continue;  }  printf("NO EXPRESSION\n");}return 0;}int dfs(long ans,int cur){if(vis[ans+32000][cur])return 0;vis[ans+32000][cur]=1;if(cur==n){if(ans==que)return 1;elsereturn 0;}if(range(ans+number[cur])&&dfs(ans+number[cur],cur+1)){record[cur]='+';return 1;}if(range(ans-number[cur])&&dfs(ans-number[cur],cur+1)){record[cur]='-';return 1;}if(range(ans*number[cur])&&dfs(ans*number[cur],cur+1)){record[cur]='*';return 1;}if(range(ans/number[cur])&&ans%number[cur]==0&&dfs(ans/number[cur],cur+1)){record[cur]='/';return 1;}return 0;}int range(long a){if(abs(a)<=32000)return 1;elsereturn 0;}