线段树 Codeforces Round #197 (Div. 2) D. Xenia and Bit Operations

题目传送门

 /*
     线段树的单点更新：有一个交叉更新，若rank=1，or；rank=0，xor
     详细解释：http://www.xuebuyuan.com/1154895.html
 */
 #include <cstdio>
 #include <iostream>
 #include <algorithm>
 #include <cstring>
 #include <string>
 #include <cmath>
 #include <set>
 #include <map>
 using namespace std;
 #define lson l, mid, rt << 1
 #define rson mid+1, r, rt << 1 | 1

 const int MAXN =  <<  | ;
 const int INF = 0x3f3f3f3f;
 struct NODE
 {
     int v, mx, mn, sum;
     int rank;
 }node[MAXN << ];

 void push_up(int rt)
 {
     if (node[rt<<].rank == )
     {
         node[rt].rank = ;
         node[rt].v = node[rt<<].v | node[rt<<|].v;
     }
     else
     {
         node[rt].rank = ;
         node[rt].v = node[rt<<].v ^ node[rt<<|].v;
     }
 }

 void build(int l, int r, int rt)
 {
     if (l == r)
     {
         scanf ("%d", &node[rt].v);
         node[rt].rank = ;
         return ;
     }
     int mid = (l + r) >> ;
     build (lson);
     build (rson);

     push_up (rt);
 }

 void updata(int p, int b, int l, int r, int rt)
 {
     if (l == r)
     {
         node[rt].v = b;
         return ;
     }
     int mid = (l + r) >> ;
     if (p <= mid)    updata (p, b, lson);
     else    updata (p, b, rson);

     push_up (rt);
 }

 int main(void)        //Codeforces Round #197 (Div. 2) D. Xenia and Bit Operations
 {
     //freopen ("H.in", "r", stdin);

     int n, m;
     scanf ("%d%d", &n, &m);
     build (, <<n, );

     int p, b;
     for (int i=; i<=m; ++i)
     {
         scanf ("%d%d", &p, &b);
         updata (p, b, , <<n, );
         printf ("%d\n", node[].v);
     }

     return ;
 }