CF
Problem - 1632C - Codeforces(枚举)（1600）
先加再按位或，一定最优
#include <bits/stdc++.h>
using namespace std;
#define LL long long
const LL mod = 998244353;
const int N=2e5+10;void solve()
{int a,b;cin >> a >> b;int ans = b-a;for (int i = a; i <= b;i++){int aa = i | b;ans = min(ans, i - a + 1 + aa - b);}for (int i = 0; i <= b - a;i++){int bb = b + i;int aa = a | bb;ans = min(ans, i + 1 + aa - bb);}cout << ans << endl;
}int main()
{ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);int T;cin >> T;while (T--){solve();}
}
Problem - 1227D1 - Codeforces（排序）（1600虚高）
#include <bits/stdc++.h>
using namespace std;
#define LL long long
const LL mod = 998244353;
const int N=105;
struct node{int num, id;
} a[N];bool cmp1(node a,node b){if(a.num!=b.num)return a.num > b.num;return a.id < b.id;
}bool cmp2(node a,node b){return a.id < b.id;
}int main()
{ios::sync_with_stdio(false);cin.tie(0);int n;cin >> n;for (int i = 0; i < n; i++){cin >> a[i].num;a[i].id = i;}int m;cin >> m;while(m--){sort(a, a + n, cmp1);int k, pos;cin >> k >> pos;sort(a, a + k, cmp2);cout << a[pos-1].num << endl;}
}
构造专题（1300）
Problem - 1902C - Codeforces(构造)
#include <bits/stdc++.h>
using namespace std;
#define LL long long
const LL mod = 998244353;
const int N=2e5+10;
LL gcd(LL a,LL b){return b?gcd(b,a%b):a;
}
LL lcm(LL a,LL b){return a/gcd(a,b)*b;
}
LL a[N];void solve()
{map<int,int> mp;int n;cin >> n;for (int i = 0; i < n;i++){cin >> a[i];mp[a[i]] = 1;}if(n==1){cout << 1 << endl;return;}sort(a, a + n);LL g = a[1] - a[0];for (int i = 2; i < n;i++){g = gcd(g, a[i] - a[i - 1]);}LL cnt = 0;for (int i = 0; i < n;i++){cnt += (a[n - 1] - a[i]) / g;}LL k = 1;while(1){//妙if(mp[a[n-1]-k*g]==0)break;k += 1;}LL ans = 1e18;//注意ans要定义为局部变量ans = min(ans, cnt + k);cout << ans << endl;
}int main()
{ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);int T;cin >> T;while (T--){solve();}
}