HDU 4620 Fruit Ninja Extreme 搜索

搜索+最优性剪枝。

DFS的下一层起点应为当前选择的 i 的下一个，即DFS(i + 1)而不是DFS( cur + 1 )，cur+1代表当前起点的下一个。没想清楚，TLE到死……

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

 using namespace std;

 const int MAXN = ;

 struct node
 {
     int t, id;
     int cnt;
     int fruit[];
 };

 int N, M, W;
 int ansN, tmpN;
 node D[MAXN];
 int tmp[MAXN];
 int ans[MAXN];
 bool vis[];

 bool cmp( node a, node b )
 {
     return a.t < b.t;
 }

 void chuli( int cnt )
 {
     for ( int i = ; i < cnt; ++i )
         ans[i] = tmp[i];
     return;
 }

 int change( int i, int *temp )
 {
     int cnt = ;
     for ( int j = ; j < D[i].cnt; ++j )
     {
         int idx = D[i].fruit[j];
         if ( !vis[ idx ] )
             temp[cnt] = idx, ++cnt;
     }
     return cnt;
 }

 void MyRestore( int *temp, int cnt )
 {

     for ( int j = ; j < cnt; ++j )
     {
         vis[ temp[j] ] = false;
     }
     return;
 }

 void DFS( int cur, int pre, int sum )
 {
     if ( tmpN > ansN )
     {
         ansN = tmpN;
         chuli( tmpN );
     }
     if ( cur >= N ) return;
     if ( tmpN + N - cur <= ansN ) return;
     if ( M - sum <  ) return;

     for ( int i = cur; i < N; ++i )
     {
         if ( pre != - && D[i].t - D[pre].t > W ) break;

         if ( D[i].cnt <  ) continue;
         int temp[];
         int left = change( i, temp );
         if ( left <  ) continue;

         for ( int j = ; j < left; ++j )
         {
             int idx = temp[j];
             vis[idx] = true;
         }

         tmp[ tmpN++ ] = D[i].id;
         DFS( i + , i, sum + left );  //i+1 不是 cur+1 !!!!!
         --tmpN;
         MyRestore( temp, left );
     }

     return;
 }

 int main()
 {
     //freopen( "1010.in", "r", stdin );
     //freopen( "s.out", "w", stdout );
     int T;
     scanf( "%d", &T );
     while ( T-- )
     {
         scanf( "%d%d%d", &N, &M, &W );
         for ( int i = ; i < N; ++i )
         {
             D[i].id = i + ;
             scanf("%d%d", &D[i].cnt, &D[i].t );
             for ( int j = ; j < D[i].cnt; ++j )
                 scanf( "%d", &D[i].fruit[j] );
         }
         sort( D, D + N, cmp );

         ansN = ;
         tmpN = ;
         memset( vis, false, sizeof(vis) );
         DFS( , -,  );

         sort( ans, ans + ansN );
         printf( "%d\n", ansN );
         for ( int i = ; i < ansN; ++i )
         {
             if ( i ) putchar(' ');
             printf( "%d", ans[i] );
         }
         puts("");
     }
     return ;
 }