UVa 10400 记忆化搜索

#include<cstdio>
#include<cstring>
#include<iostream>
#include<algorithm>
using namespace std;

const int INF = 32000;
const int maxn = 105;

int a[maxn];
char ans[maxn]; //a[i] = 1代表+，2代表-，3代表*，4代表/  ;
int len,goal;
bool vis[maxn][INF+1][2];  //  vis[i][j][1]=1 表示计算完前i个数字的某种组合可以得到正j，dp[i][j][0]=1则为负j

bool dfs(int u,int sum){
    if(u == 1){
        if(a[1] == sum ) return true;
        else             return false;
    }

    if(sum >= 0 && vis[u][sum][1])
      return false;

    else if(sum<0 && vis[u][-sum][0])
      return false;



    int temp = sum - a[u];
    if(temp > -INF && temp < INF){
        ans[u] = '+';
        if(dfs(u-1,temp))   return true;
        if(temp >= 0){
            vis[u-1][temp][1] = true;
        }
        else{
            vis[u-1][-temp][0] = true;
        }
    }
    temp = sum + a[u];
    if(temp > -INF && temp < INF){
        ans[u] = '-';
        if(dfs(u-1,temp))   return true;
        if(temp >= 0){
            vis[u-1][temp][1]  = true;
        }
        else{
            vis[u-1][-temp][0] = true;
        }
    }
    temp = sum * a[u];
    if(temp > -INF && temp < INF){
        ans[u] = '/';
        if(dfs(u-1,temp))   return true;
        if(temp >= 0){
            vis[u-1][temp][1]  = true;
        }
        else{
            vis[u-1][-temp][0] = true;
        }
    }
    if(sum % a[u]) return false;
    temp = sum / a[u];
    if(temp > -INF && temp < INF){
        ans[u] = '*';
        if(dfs(u-1,temp))   return true;
        if(temp >= 0){
            vis[u-1][temp][1]  = true;
        }
        else{
            vis[u-1][-temp][0] = true;
        }
    }
    return  false;
}
void print(){
    ans[len+1] = '=';
    for(int i=1;i<=len;i++){
        printf("%d%c",a[i],ans[i+1]);
    }
    printf("%d
",goal);
}
int main()
{
   //freopen("E:\acm\input.txt","r",stdin);
    int T;
    cin>>T;
    while(T--){
        scanf("%d",&len);
        for(int i=1;i<=len;i++)
            scanf("%d",&a[i]);
        scanf("%d",&goal);

        memset(vis,0,sizeof(vis));

        if(dfs(len,goal)){
            print();
        }
        else
            printf("NO EXPRESSION
");
    }
}