hdu 1556 线段树

这个题其实有O(n)的算法，不过还是用线段树做了一遍，还写了个自认为不错的pushalldown函数，哈哈。

 1 #include <iostream>
 2 #include <cstring>
 3 #include <cstdio>
 4 using namespace std;
 5
 6 const int N = 100001;
 7 int ans[N];
 8
 9 struct Node
10 {
11     int l, r, add;
12 } node[N << 2];
13
14 void build( int i, int l, int r )
15 {
16     node[i].l = l, node[i].r = r, node[i].add = 0;
17     if ( l == r ) return ;
18     int lc = i << 1, rc = lc | 1, mid = ( l + r ) >> 1;
19     build( lc, l, mid );
20     build( rc, mid + 1, r );
21 }
22
23 void pushdown( int i )
24 {
25     if ( node[i].add )
26     {
27         int lc = i << 1, rc = lc | 1;
28         node[lc].add += node[i].add;
29         node[rc].add += node[i].add;
30         node[i].add = 0;
31     }
32 }
33
34 void update( int i, int l, int r )
35 {
36     if ( node[i].l == l && node[i].r == r )
37     {
38         node[i].add++;
39         return ;
40     }
41     //可以最后一起放下来
42     //pushdown(i);
43     int lc = i << 1, rc = lc | 1, mid = ( node[i].l + node[i].r ) >> 1;
44     if ( r <= mid )
45     {
46         update( lc, l, r );
47     }
48     else if ( l > mid )
49     {
50         update( rc, l, r );
51     }
52     else
53     {
54         update( lc, l, mid );
55         update( rc, mid + 1, r );
56     }
57 }
58
59 void pushalldown( int i )
60 {
61     if ( node[i].l == node[i].r )
62     {
63         ans[node[i].l] = node[i].add;
64         return ;
65     }
66     pushdown(i);
67     pushalldown( i << 1 );
68     pushalldown( i << 1 | 1 );
69 }
70
71 int main ()
72 {
73     int n;
74     while ( scanf("%d", &n), n )
75     {
76         build( 1, 1, n );
77         for ( int i = 1; i <= n; i++ )
78         {
79             int a, b;
80             scanf("%d%d", &a, &b);
81             update( 1, a, b );
82         }
83         pushalldown(1);
84         for ( int i = 1; i <= n; i++ )
85         {
86             printf("%d", ans[i]);
87             if ( i != n ) putchar(‘ ‘);
88             else putchar(‘\n‘);
89         }
90     }
91     return 0;
92 }