Educational Codeforces Round 122 (Rated for Div. 2) ABC

Problem - A - Codeforces

The main idea of the topic ： Put an integer n, Change its lowest digit to make it 7 Multiple .

Note that the need cannot contain a preamble 0.

 input

3
42
23
377

output

42
28
777

  Directly control its lowest position without crossing the boundary .

#include<iostream>
#include<cmath>
#include<string>
#include<cstring>
#include<cstdlib>
#include<algorithm>
using namespace std;
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    int t,n,m;
    cin>>t;
    while(t--)
    {
        int n;
        cin>>n;
        if(n%7==0) cout<<n<<endl;
        else
        {
            if(n%10>=n%7) cout<<n-n%7<<endl;
            else cout<<n+(7-n%7)<<endl;
        }
    }
    return 0;
}

Problem - B - Codeforces

The main idea of the topic ： Given one, only 0 and 1 Composed string s, Select a substring , If 0 The number of >1, Then delete 1 The number of , On the contrary, if 1 The number of >0, Then delete 0 The number of .

a key （wa spot ） coming ：If the amounts are the same, do nothing.

input

4
01
1010101010111
00110001000
1

output

0
5
3
0

 If the amounts are the same, do nothing. If sum0==sum1, Don't do anything ？

WA Once + Read the title again and find ： Select substring , You have to delete the maximum number , So if I have a string s：“010101”

If I choose the whole string , You can only get 0

However, if I choose a string from it “01010”, Successfully found the difference between size ,so↓

#include<iostream>
#include<cmath>
#include<string>
#include<cstring>
#include<cstdlib>
#include<algorithm>
using namespace std;
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    int t,n,m;
    cin>>t;
    while(t--)
    {
        string s;
        cin>>s;
        int one=0,zero=0;
        for(int i=0;i<s.size();i++)
        {
            if(s[i]=='0') zero++;
            else one++;
        }
        if(zero==one) cout<<zero-1<<endl;
        else cout<<min(zero,one)<<endl;
    }
    return 0;
}

Problem - C - Codeforces

The main idea of the topic ： Game character health hc, aggressivity dc; Monster health hm, aggressivity dm.

The roles before the war are k A coin , One coin can be purchased separately w Attack power , Or is it a The life value of the .

Ask the character if he can win the monster ？

input

4
25 4
9 20
1 1 10
25 4
12 20
1 1 10
100 1
45 2
0 4 10
9 2
69 2
4 2 7

output

YES
NO
YES
YES

Be careful ： If the judgment condition is written ca/d>=c/cb Meeting wa. And write it （ The life value of the character + The attack power of monsters -1）/ The attack power of monsters >=（ Monster health + The attack power of the character -1）/ The attack power of the character . Because we will encounter the problem of remainder , So you need to round up ceil

eg：(5+2-1)/2=3     5/2=2;

#include<iostream>
#include<cmath>
#include<string>
#include<cstring>
#include<cstdlib>
#include<algorithm>
using namespace std;
typedef long long LL;
int main()
{
    cin.tie(0); cout.tie(0); ios::sync_with_stdio(false);
    int t;
    cin>>t;
    while(t--)
    {
        LL a,b,c,d,k,bb,aa;
        cin>>a>>b>>c>>d>>k>>bb>>aa;
        bool flag=false;
        for(LL i=0;i<=k;i++)
        {
            LL ca=a+i*aa;
            LL cb=b+(k-i)*bb;
            //cout<<ca<<" "<<cb<<" "<<c<<" "<<d;
            if((ca+d-1)/d>=(cb+c-1)/cb)
            {
                flag=true;
                cout<<"YES"<<endl;
                break;
            }
        }
        if(flag==false) cout<<"NO"<<endl;
    }
    return 0;
}