uva10400 Game Show Math（DP）

题目链接：http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=11&page=show_problem&problem=1341

注意除以0和溢出的情况

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int dp[110][64000];
int a[110],n,x,k,ans[110];
int main(){
    int t;
    cin>>t;
    while(t--){
        cin>>n;
        for(int i=0;i<n;i++) cin>>a[i];
        memset(dp,0,sizeof dp);
        cin>>x;
        dp[0][a[0]+32000]=1;
        for(int i=1;i<n;i++){
            for(int j=-32000;j<=32000;j++){
                for(int k=1;k<=4;k++){
                    if(k==1){
                        if(j+a[i]<-32000||j+a[i]>32000) continue;
                        if(dp[i-1][j+32000]) dp[i][j+a[i]+32000]=k;
                    }else if(k==2){
                        if(j-a[i]<-32000||j-a[i]>32000) continue;
                        if(dp[i-1][j+32000]) dp[i][j-a[i]+32000]=k;
                    }else if(k==3){
                        if(j*a[i]<-32000||j*a[i]>32000) continue;
                        if(dp[i-1][j+32000]) dp[i][j*a[i]+32000]=k;
                    }else{
                        if(a[i]==0) continue;
                        if(j/a[i]<-32000||j/a[i]>32000) continue;
                        if(j%a[i]!=0) continue;
                        if(dp[i-1][j+32000]) dp[i][j/a[i]+32000]=k;
                    }
                }
            }
        }
        if(dp[n-1][x+32000]){
            k=0;
            int now=x;
            for(int i=n-2;i>=0;i--){
               for(int j=1;j<=4;j++){
                  if(j==1){
                      if(dp[i][now-a[i+1]+32000]) {ans[i+1]=1;now-=a[i+1];break;}
                  }else if(j==2){
                      if(dp[i][now+a[i+1]+32000]) {ans[i+1]=2;now+=a[i+1];break;}
                  }else if(j==3){
                      if(a[i]==0) {ans[i]=j;now=a[i];break;}
                      if(dp[i][now/a[i+1]+32000]) {ans[i+1]=3;now/=a[i+1];break;}
                  }else{
                      if(dp[i][now*a[i+1]+32000]) {ans[i+1]=4;now*=a[i+1];break;}
                  }
               }
            }
            cout<<a[0];
            for(int i=1;i<n;i++){
               if(ans[i]==1) cout<<"+";
               else if(ans[i]==2) cout<<"-";
               else if(ans[i]==3) cout<<"*";
               else cout<<"/";
               cout<<a[i];
            }
            cout<<"="<<x;
            cout<<endl;
        }else{
            cout<<"NO EXPRESSION"<<endl;
        }
    }
    return 0;
}