原题题目
代码实现(首刷看了点人家的思路)
class Solution {
public:
class Solution {
public:bool canArrange(vector<int>& arr, int k) {
vector<int> v(k,0);for(auto& num:arr){
num = num%k;if(num<0) ++v[k+num];else ++v[num];}for(int i=1;i<v.size();++i)if(v[k-i] != v[i]) return false;return v[0]%2==0;}
};