HDU 1540 Tunnel Warfare

线段树点修改+区间合并

对于如何查询连续某块的端点和长度还不太熟……但是属于经典常见操作。

 

  1 #include <cstdio>

  2 #include <cstring>

  3 #include <cstdlib>

  4 #include <algorithm>

  5 

  6 using namespace std;

  7 

  8 #define lc rt << 1

  9 #define rc rt << 1 | 1

 10 #define lson l, m, rt << 1

 11 #define rson m + 1, r, rt << 1 | 1

 12 

 13 const int MAXN = 50002;

 14 

 15 int N, Q;

 16 int stack[MAXN];

 17 int top;

 18 int len[ MAXN << 2 ];

 19 int Llen[ MAXN << 2 ];

 20 int Rlen[ MAXN << 2 ];

 21 bool lbd[ MAXN << 2 ];

 22 bool rbd[ MAXN << 2 ];

 23 

 24 void PushUp( int rt, int l, int r, int m )

 25 {

 26     len[rt] = max( len[lc], len[rc] );

 27     if ( rbd[lc] && lbd[rc] )

 28         len[rt] = max( len[rt], Llen[rc] + Rlen[lc] );

 29 

 30     lbd[rt] = lbd[lc];

 31     rbd[rt] = rbd[rc];

 32 

 33     Llen[rt] = Llen[lc];

 34     Rlen[rt] = Rlen[rc];

 35 

 36     if ( Llen[lc] == m - l + 1 ) Llen[rt] += Llen[rc];

 37     if ( Rlen[rc] == r - m ) Rlen[rt] += Rlen[lc];

 38 

 39     return;

 40 }

 41 

 42 void build( int l, int r, int rt )

 43 {

 44     if ( l == r )

 45     {

 46         lbd[rt] = rbd[rt] = true;

 47         len[rt] = 1;

 48         Llen[rt] = Rlen[rt] = 1;

 49         return;

 50     }

 51 

 52     int m = ( l + r ) >> 1;

 53     build( lson );

 54     build( rson );

 55     PushUp( rt, l, r, m );

 56     return;

 57 }

 58 

 59 void Update( int L, int c, int l, int r, int rt )

 60 {

 61     if ( L == l && L == r )

 62     {

 63         len[rt] = Llen[rt] = Rlen[rt] = c;

 64         if ( c == 1 ) lbd[rt] = rbd[rt] = true;

 65         else lbd[rt] = rbd[rt] = false;

 66         return;

 67     }

 68 

 69     int m = ( l + r ) >> 1;

 70     if ( L <= m ) Update( L, c, lson );

 71     else Update( L, c, rson );

 72     PushUp( rt, l, r, m );

 73 

 74     return;

 75 }

 76 

 77 int Query( int L, int l, int r, int rt )

 78 {

 79     if ( l == r || !len[rt] || len[rt] == r - l + 1 ) return len[rt];

 80     int m = ( l + r ) >> 1;

 81     if ( L <= m )

 82     {

 83         if ( L > m - Rlen[lc] ) return Query( L, lson ) + Query( m + 1, rson );

 84         else return Query( L, lson );

 85     }

 86     else

 87     {

 88         if ( L < m + 1 + Llen[rc] ) return Query( m, lson ) + Query( L, rson );

 89         else return Query( L, rson );

 90     }

 91 }

 92 

 93 int main()

 94 {

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

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

 97     while ( ~scanf( "%d%d", &N, &Q ) )

 98     {

 99         build( 1, N, 1 );

100         top = 0;

101         while ( Q-- )

102         {

103             char str[4];

104             scanf( "%s", str );

105             if ( str[0] == 'R' )

106             {

107                 if ( top > 0 )

108                     Update( stack[top--], 1, 1, N, 1 );

109             }

110             else

111             {

112                 int a;

113                 scanf( "%d", &a );

114                 if ( str[0] == 'D' )

115                 {

116                     Update( a, 0, 1, N, 1 );

117                     stack[ ++top ] = a;

118                 }

119                 else

120                     printf( "%d\n", Query( a, 1, N, 1 ) );

121             }

122         }

123     }

124     return 0;

125 }