题目传送门
1 /*
2 线段树的单点更新：有一个交叉更新，若rank=1，or；rank=0，xor
3 详细解释：http://www.xuebuyuan.com/1154895.html
4 */
5 #include <cstdio>
6 #include <iostream>
7 #include <algorithm>
8 #include <cstring>
9 #include <string>
10 #include <cmath>
11 #include <set>
12 #include <map>
13 using namespace std;
14 #define lson l, mid, rt << 1
15 #define rson mid+1, r, rt << 1 | 1
16
17 const int MAXN = 1 << 17 | 1;
18 const int INF = 0x3f3f3f3f;
19 struct NODE
20 {
21 int v, mx, mn, sum;
22 int rank;
23 }node[MAXN << 2];
24
25 void push_up(int rt)
26 {
27 if (node[rt<<1].rank == 1)
28 {
29 node[rt].rank = 0;
30 node[rt].v = node[rt<<1].v | node[rt<<1|1].v;
31 }
32 else
33 {
34 node[rt].rank = 1;
35 node[rt].v = node[rt<<1].v ^ node[rt<<1|1].v;
36 }
37 }
38
39
40 void build(int l, int r, int rt)
41 {
42 if (l == r)
43 {
44 scanf ("%d", &node[rt].v);
45 node[rt].rank = 1;
46 return ;
47 }
48 int mid = (l + r) >> 1;
49 build (lson);
50 build (rson);
51
52 push_up (rt);
53 }
54
55 void updata(int p, int b, int l, int r, int rt)
56 {
57 if (l == r)
58 {
59 node[rt].v = b;
60 return ;
61 }
62 int mid = (l + r) >> 1;
63 if (p <= mid) updata (p, b, lson);
64 else updata (p, b, rson);
65
66 push_up (rt);
67 }
68
69
70 int main(void) //Codeforces Round #197 (Div. 2) D. Xenia and Bit Operations
71 {
72 //freopen ("H.in", "r", stdin);
73
74 int n, m;
75 scanf ("%d%d", &n, &m);
76 build (1, 1<<n, 1);
77
78 int p, b;
79 for (int i=1; i<=m; ++i)
80 {
81 scanf ("%d%d", &p, &b);
82 updata (p, b, 1, 1<<n, 1);
83 printf ("%d
", node[1].v);
84 }
85
86 return 0;
87 }