poj 2104 划分树模板

划分树的模板题。

 1 #include <iostream>

 2 #include <algorithm>

 3 #include <cstdio>

 4 using namespace std;

 5 

 6 const int N = 100001;

 7 int tree[20][N];

 8 int sum[20][N];

 9 int as[N];

10 

11 void build( int p, int l, int r )

12 {

13     int mid = ( ( l + r ) >> 1 );

14     int lm = 0, ls = l, rs = mid + 1;

15     for ( int i = mid; i >= l; i-- )

16     {

17         if ( as[i] == as[mid] )

18             lm++;

19         else

20             break;

21     }

22     for ( int i = l; i <= r; i++ )

23     {

24         if ( i == l )

25             sum[p][i] = 0;

26         else

27             sum[p][i] = sum[p][i - 1];

28         if ( tree[p][i] == as[mid] )

29         {

30             if ( lm )

31             {

32                 lm--;

33                 sum[p][i]++;

34                 tree[p + 1][ls++] = tree[p][i];

35             }

36             else

37             {

38                 tree[p + 1][rs++] = tree[p][i];

39             }

40         }

41         else if ( tree[p][i] < as[mid] )

42         {

43             sum[p][i]++;

44             tree[p + 1][ls++] = tree[p][i];

45         }

46         else

47         {

48             tree[p + 1][rs++] = tree[p][i];

49         }

50     }

51     if ( l == r )

52         return ;

53     build( p + 1, l, mid );

54     build( p + 1, mid + 1, r );

55 }

56 

57 int query( int p, int l, int r, int ql, int qr, int k )

58 {

59     if ( l == r )

60         return tree[p][l];

61     int mid = ( ( l + r ) >> 1 );

62     int s, ss;

63     if ( ql == l )

64         s = 0, ss = sum[p][qr];

65     else

66         s = sum[p][ql - 1], ss = sum[p][qr] - s;

67     if ( k <= ss )

68         return query( p + 1, l, mid, l + s, l + sum[p][qr] - 1, k );

69     else

70         return query( p + 1, mid + 1, r, mid + 1 - l + ql - s, mid + 1 - l + qr - sum[p][qr], k - ss );

71 }

72 

73 int main ()

74 {

75     int n, m;

76     while ( scanf("%d%d", &n, &m) != EOF )

77     {

78         for ( int i = 1; i <= n; i++ )

79         {

80             scanf("%d", as + i);

81             tree[0][i] = as[i];

82         }

83         sort( as + 1, as + 1 + n );

84         build( 0, 1, n );

85         while ( m-- )

86         {

87             int a, b, c;

88             scanf("%d%d%d", &a, &b, &c);

89             printf("%d\n", query( 0, 1, n, a, b, c ));

90         }

91     }

92     return 0;

93 }