与运算
0&n=0

1&奇数=1

1&偶数=0

#include <bits/stdc++.h>
//dfs 大法师
#define ll long long
using namespace std;
const int mod=20100403;
const int Inf=0x3f3f3f3f;
inline int read()
{int x=0,f=1;char ch=getchar();while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}return x*f;
}int m1[]={0,31,28,31,30,31,30,31,31,30,31,30,31};
int m2[]={0,31,29,31,30,31,30,31,31,30,31,30,31};
void Get_Time()
{time_t timep;time(&timep); //获取从1970至今过了多少秒，存入time_t类型的timepprintf("%s", ctime(&timep));//用ctime将秒数转化成字符串格式，输出：Thu Feb 28 14:14:17 2019
}
void solve()
{int t;cin>>t;while(t--){ll n,k;cin>>n>>k;if(n==4&&k==3){cout<<-1<<endl;continue;}ll d=n-1-k;if(k==n-1){cout<<k<<" "<<k-1<<endl;cout<<0<<" "<<n-1-3<<endl;cout<<1<<" "<<3<<endl;for(int a=0;a<n/2;a++){if(a!=0&&a!=1&&a!=n-k&&a!=3)cout<<a<<" "<<n-1-a<<endl;}}elseif(k!=0){cout<<0<<" "<<d<<endl;cout<<k<<" "<<n-1<<endl;for(int a=0;a<n/2;a++){if(a!=0&&a!=k&&a!=n-1-k)cout<<a<<" "<<n-1-a<<endl;}}else{for(int a=0;a<n/2;a++)cout<<a<<" "<<n-1-a<<endl;}}
}
signed main()
{ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);solve();return 0;
}

或运算

#include<bits/stdc++.h>
using namespace std;
int n;
int main(){int t;cin>>t;while(t--){int a,b;cin>>a>>b;int ans=b-a;if((b|a)==b){puts("1");continue;}for(int i=1;i+1<=ans;i++){if(((a+i)|b)==b||((b+i)|a)==b+i) ans=i+1;}cout<<ans<<endl;}
}