CF959F.Mahmoud and Ehab and yet another xor task
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题目描述
Ehab has an array a of n integers. He likes the bitwise-xor operation and he likes to bother Mahmoud so he came up with a problem. He gave Mahmoud q queries. In each of them, he gave Mahmoud 2 integers l and x , and asked him to find the number of subsequences of the first l elements of the array such that their bitwise-xor sum is x . Can you help Mahmoud answer the queries?
A subsequence can contain elements that are not neighboring.
输入格式
The first line contains integers n and q (1<=n,q<=105) , the number of elements in the array and the number of queries.
The next line contains n integers a1 , a2 , ... , an (0<=ai<220) , the elements of the array.
The next q lines, each contains integers l and x (1<=l<=n , 0<=x<220) , representing the queries.
输出格式
For each query, output its answer modulo 109+7 in a newline.
输入输出样例
输入#1
5 5 0 1 2 3 4 4 3 2 0 3 7 5 7 5 8
输出#1
4 2 0 4 0
输入#2
3 2 1 1 1 3 1 2 0
输出#2
4 2
说明/提示
The bitwise-xor sum of the empty set is 0 and the bitwise-xor sum of a set containing one element is that element itself.