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……

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <cstdlib>

  4 #include <algorithm>

  5 

  6 using namespace std;

  7 

  8 const int MAXN = 40;

  9 

 10 struct node

 11 {

 12     int t, id;

 13     int cnt;

 14     int fruit[12];

 15 };

 16 

 17 int N, M, W;

 18 int ansN, tmpN;

 19 node D[MAXN];

 20 int tmp[MAXN];

 21 int ans[MAXN];

 22 bool vis[320];

 23 

 24 bool cmp( node a, node b )

 25 {

 26     return a.t < b.t;

 27 }

 28 

 29 void chuli( int cnt )

 30 {

 31     for ( int i = 0; i < cnt; ++i )

 32         ans[i] = tmp[i];

 33     return;

 34 }

 35 

 36 int change( int i, int *temp )

 37 {

 38     int cnt = 0;

 39     for ( int j = 0; j < D[i].cnt; ++j )

 40     {

 41         int idx = D[i].fruit[j];

 42         if ( !vis[ idx ] )

 43             temp[cnt] = idx, ++cnt;

 44     }

 45     return cnt;

 46 }

 47 

 48 void MyRestore( int *temp, int cnt )

 49 {

 50     

 51     for ( int j = 0; j < cnt; ++j )

 52     {

 53         vis[ temp[j] ] = false;

 54     }

 55     return;

 56 }

 57 

 58 void DFS( int cur, int pre, int sum )

 59 {

 60     if ( tmpN > ansN )

 61     {

 62         ansN = tmpN;

 63         chuli( tmpN );

 64     }

 65     if ( cur >= N ) return;

 66     if ( tmpN + N - cur <= ansN ) return;

 67     if ( M - sum < 3 ) return;

 68 

 69     for ( int i = cur; i < N; ++i )

 70     {

 71         if ( pre != -1 && D[i].t - D[pre].t > W ) break;

 72 

 73         if ( D[i].cnt < 3 ) continue;

 74         int temp[20];

 75         int left = change( i, temp );

 76         if ( left < 3 ) continue;

 77 

 78         for ( int j = 0; j < left; ++j )

 79         {

 80             int idx = temp[j];

 81             vis[idx] = true;

 82         }

 83 

 84         tmp[ tmpN++ ] = D[i].id;

 85         DFS( i + 1, i, sum + left );  //i+1 不是 cur+1 !!!!!

 86         --tmpN;

 87         MyRestore( temp, left );

 88     }

 89 

 90     return;

 91 }

 92 

 93 int main()

 94 {

 95     //freopen( "1010.in", "r", stdin );

 96     //freopen( "s.out", "w", stdout );

 97     int T;

 98     scanf( "%d", &T );

 99     while ( T-- )

100     {

101         scanf( "%d%d%d", &N, &M, &W );

102         for ( int i = 0; i < N; ++i )

103         {

104             D[i].id = i + 1;

105             scanf("%d%d", &D[i].cnt, &D[i].t );

106             for ( int j = 0; j < D[i].cnt; ++j )

107                 scanf( "%d", &D[i].fruit[j] );

108         }

109         sort( D, D + N, cmp );

110 

111         ansN = 0;

112         tmpN = 0;

113         memset( vis, false, sizeof(vis) );

114         DFS( 0, -1, 0 );

115 

116         sort( ans, ans + ansN );

117         printf( "%d\n", ansN );

118         for ( int i = 0; i < ansN; ++i )

119         {

120             if ( i ) putchar(' ');

121             printf( "%d", ans[i] );

122         }

123         puts("");

124     }

125     return 0;

126 }