[Codeforces 339D] Xenia and Bit Operations

[题目链接]

https://codeforces.com/problemset/problem/339/D

[算法]

线段树模拟即可

时间复杂度 ：O(MN)

[代码]

#include<bits/stdc++.h>
using namespace std;
#define MAXN 18
const int MAXS =  << MAXN;

int n , m;
int a[MAXS];

struct SegmentTree
{
        struct Node
        {
                int l , r;
                int value , d;
        }    Tree[MAXS << ];
        inline void update(int index)
        {
                if (Tree[index].d == ) Tree[index].value = Tree[index << ].value | Tree[index <<  | ].value;
                else Tree[index].value = Tree[index << ].value ^ Tree[index <<  | ].value;
        }
        inline void build(int index,int l,int r)
        {
                Tree[index].l = l;
                Tree[index].r = r;
                if (l == r)
                {
                        Tree[index].value = a[l];
                        Tree[index].d = ;
                        return;
                }
                int mid = (l + r) >> ;
                build(index << ,l,mid);
                build(index <<  | ,mid + ,r);
                Tree[index].d = (Tree[index << ].d + ) % ;
                update(index);
        }
        inline void modify(int index,int pos,int val)
        {
                if (Tree[index].l == Tree[index].r)
                {
                        Tree[index].value = val;
                        return;
                }
                int mid = (Tree[index].l + Tree[index].r) >> ;
                if (mid >= pos) modify(index << ,pos,val);
                else modify(index <<  | ,pos,val);
                update(index);
        }
        inline int query()
        {
                return Tree[].value;
        }
} T;

template <typename T> inline void read(T &x)
{
    T f = ; x = ;
    char c = getchar();
    for (; !isdigit(c); c = getchar()) if (c == '-') f = -f;
    for (; isdigit(c); c = getchar()) x = (x << ) + (x << ) + c - '';
    x *= f;
}

int main()
{

        read(n); read(m);
        for (int i = ; i <= ( << n); i++) read(a[i]);
        T.build(,,( << n));
        while (m--)
        {
                int x , y;
                read(x); read(y);
                T.modify(,x,y);
                printf("%d\n",T.query());
        }

        return ;

}