递推DP URAL 1244 Gentlemen

题目传送门

 /*
     题意：给出少了若干卡片后的总和，和原来所有卡片，问少了哪几张
     DP：转化为少了的总和是否能有若干张卡片相加得到，dp[j+a[i]] += dp[j];
         记录一次路径，当第一次更新的时候
 */
 #include <cstdio>
 #include <iostream>
 #include <algorithm>
 #include <cmath>
 #include <cstring>
 #include <vector>
 #include <stack>
 using namespace std;

 const int MAXN = 1e5 + ;
 const int INF = 0x3f3f3f3f;
 int a[MAXN];
 int dp[MAXN];
 int rt[MAXN];

 int main(void)        //URAL 1244 Gentlemen
 {
     //freopen ("U.in", "r", stdin);

     int tot, n;
     while (scanf ("%d", &tot) == )
     {
         scanf ("%d", &n);
         int sum = ;
         for (int i=; i<=n; ++i)    {scanf ("%d", &a[i]);    sum += a[i];}
         if (tot > sum)    {puts ("");    continue;}

         memset (rt, , sizeof (rt));
         memset (dp, , sizeof (dp));
         sum -= tot;
         dp[] = ;
         for (int i=; i<=n; ++i)
         {
             for (int j=sum-a[i]; j>=; --j)
             {
                 if (dp[j] && dp[j+a[i]] == )
                 {
                     rt[j+a[i]] = i;
                 }
                 dp[j+a[i]] += dp[j];
             }
         }

         if (dp[sum] == )    {puts ("");    continue;}
         else if (dp[sum] == )
         {
             vector<int> ans;
             for (int i=n; i>=; --i)
             {
                 if (rt[sum] == i)    {ans.push_back (i);    sum -= a[i];}
             }
             for (int i=ans.size ()-; i>=; --i)    printf ("%d%c", ans[i], (i==) ? '\n' : ' ');
         }
         else    puts ("-1");
     }

     return ;
 }