Educational Codeforces Round 23

A题

分析：注意两个点之间的倍数差，若为偶数则为YES，否则为NO

#include "iostream"
#include "cstdio"
#include "cstring"
#include "string"
#include "cmath"
using namespace std;
int main()
{
    int x1,y1,x2,y2;
    cin>>x1>>y1>>x2>>y2;
    int x,y;
    cin>>x>>y;
    int cnt1=x2-x1;
    int cnt2=y2-y1;
    int flag=0;
    if(cnt1%x){
        flag=1;
    }
    if(cnt2%y){
        flag=1;
    }
    if(abs(abs(cnt1/x)-abs(cnt2/y))%2){
        flag=1;
    }
    if(!flag){
        cout<<"YES"<<endl;
    }else{
        cout<<"NO"<<endl;
    }
}

B题

分析：先看只用第一个数是否满足情况，如果不行在加入第二个数，不行在加入第三个数，如此分别统计三种情况即可

#include "iostream"
#include "cstdio"
#include "cstring"
#include "string"
#include "algorithm"
#include "set"
#include "vector"
using namespace std;
const int maxn=100000+10;
long long a[maxn];
int n;
long long solve3(long long sum){
    return (sum*(sum-1)*(sum-2)/6);
}
long long solve2(long long sum){
    return (sum*(sum-1)/2);
}
int main()
{
    cin>>n;
    for(int i=0;i<n;i++)
        cin>>a[i];
    sort(a,a+n);
    set<long long>h;
    for(int i=0;i<n;i++){
        h.insert(a[i]);
    }
    set<long long>::iterator it;
    vector<long long>q;
    for(it=h.begin();it!=h.end();it++){
        q.push_back(*it);
    }
    long long cnt1=0,cnt2=0,cnt3=0;
    for(int i=0;i<n;i++){
        if(a[i]==q[0]){
            cnt1++;
        }else if(a[i]==q[1]){
            cnt2++;
        }else if(a[i]==q[2]){
            cnt3++;
        }
    }
    if(cnt1>=3){
        cout<<solve3(cnt1)<<endl;
    }else if(cnt1==2){
        cout<<cnt2<<endl;
    }else{
        if(cnt2>=2){
            cout<<solve2(cnt2)<<endl;
        }else{
            cout<<cnt3<<endl;
        }
    }
    return 0;
}

C题

分析：因为两个数的差值最大不会超过18*9=162，所以直接暴力即可

#include "iostream"
#include "cstdio"
#include "cstring"
using namespace std;
long long a,b;
long long solve(long long num){
    long long ans=0;
    while(num){
        long long mod=num%10;
        ans+=mod;
        num/=10;
    }
    return ans;
}
int main()
{
    cin>>b>>a;
    long long sum=b-a;
    if(sum<=0){
        cout<<"0"<<endl;
        return 0;
    }
    long long cnt=0;
    if(b-a<=162){
        for(long long i=a;i<=b;i++){
            long long tt=i;
            //cout<<b-solve(tt)<<endl;
            if((i-solve(tt))>=a)
                cnt++;
        }
        cout<<cnt<<endl;
    }else{
        for(long long i=a;i<=a+162;i++){
            long long yy=i;
            if((i-solve(yy))<a)
                cnt++;
        }
        cout<<sum-cnt+1<<endl;
    }
    return 0;
}