hdu1166 单点更新

第一道线段树，对着学长给的板子敲，嘿嘿，纪念一下~~~

代码：

 1 #include <cstdio>
 2 #include <iostream>
 3 #include <cstring>
 4 #include <string.h>
 5 #include <cmath>
 6 #include <cstdlib>
 7 #include <algorithm>
 8
 9 using namespace std;
10
11 const int maxn = 50000 + 10;
12 int a[maxn];
13
14 struct node
15 {
16     int left, right, sum;
17 } b[maxn*4];
18
19 void build(int left, int right, int i)
20 {
21     b[i].left = left;
22     b[i].right = right;
23     int mid = (left + right)/2;
24     if(left == right) {
25         b[i].sum = a[left];
26         return ;
27     }
28     build(left, mid, 2*i);
29     build(mid+1, right, 2*i+1);
30     b[i].sum = b[2*i].sum + b[2*i+1].sum;
31 }
32
33 void Add(int id, int num, int i)
34 {
35     if(b[i].left == b[i].right) {
36         b[i].sum += num;
37         return ;
38     }
39     else {
40         b[i].sum += num;
41         if(id <= b[2*i].right) Add(id, num, 2*i);
42         else Add(id, num, 2*i+1);
43     }
44 }
45
46 int Query(int left, int right, int i)
47 {
48     int mid;
49     if(left == b[i].left && right == b[i].right) {
50         return b[i].sum;
51     }
52     mid = (b[i].left + b[i].right)/2;
53     if(right <= mid) return Query(left, right, 2*i);
54     else if(left > mid) return Query(left, right, 2*i+1);
55     else return Query(left, mid, 2*i) + Query(mid+1, right, 2*i+1);
56 }
57
58 int main()
59 {
60     //freopen("test.in", "r", stdin);
61     char s[10];
62     int T, N, x, y;
63     scanf("%d", &T);
64     int t = T;
65     while(T--)
66     {
67         printf("Case %d:\n", t-T);
68         scanf("%d", &N);
69         for(int i = 1; i <= N; i++)
70             scanf("%d", &a[i]);
71         build(1, N, 1);
72         while(1) {
73             scanf("%s", s);
74             if(s[0] == ‘E‘) break;
75             scanf("%d%d", &x, &y);
76             if(s[0] == ‘Q‘) printf("%d\n", Query(x, y, 1));
77             else if(s[0] == ‘A‘) Add(x, y, 1);
78             else Add(x, -y, 1);
79         }
80     }
81     return 0;
82 }

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