[POJ 2397] Spiderman

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <algorithm>

using namespace std;
const int INF=0x3f3f3f3f;
int T,n,d,dp[55][1005],pre[55][1005];

void print(int cur,int h)
{
    if(pre[cur][h]==INF || cur<0) return;
    print(cur-1,pre[cur][h]);
    printf("%c",(pre[cur][h]>h)?‘D‘:‘U‘);
}

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d",&n);
        memset(dp,0x3f,sizeof(dp));memset(pre,0x3f,sizeof(pre));
        dp[0][0]=0;
        for(int i=0;i<n;i++)
        {
            scanf("%d",&d);
            for(int j=0;j<=1000;j++)
            {
                if(dp[i][j]==INF) continue;
                if(j+d<=1000 && dp[i+1][j+d]>max(dp[i][j],j+d))
                    dp[i+1][j+d]=max(dp[i][j],j+d),pre[i+1][j+d]=j;
                if(j-d>=0 && dp[i+1][j-d]>dp[i][j])
                    dp[i+1][j-d]=dp[i][j],pre[i+1][j-d]=j;
            }
        }
        if(dp[n][0]==INF) puts("IMPOSSIBLE");
        else print(n,0),puts("");
    }
    return 0;
}