Codeforces Round #719 (Div. 3)（a，b，c）

「爱情、让人受尽委屈。」 2023-01-19 07:29 46阅读 0赞

[题目https://codeforc.es/contest/1520][https_codeforc.es_contest_1520]

### 简单题 ###

*  a
 *  b
 *  c

# a #

一个字符串，出现在一个地方的字符，不能再第二个地方出现

A A A A Z A A A A A AAAAZAAAAA AAAAZAAAAA \-------NO  
 F F G Z Z Z Y FFGZZZY FFGZZZY \------------- YES

#include<bits/stdc++.h>
    #define ll long long 
    using namespace std;
    
    const int N = 1e4;
    
    int u[N+10], s[N+10];
    
    void solve()
    { 
        int n; cin >> n; 
        string str; cin >> str;
        if (n == 1) puts("YES"),return;
        
        char ch;
        for (int i = 0; i < n; i++)
        { 
            if (str[i] != str[i+1]) 
            { 
                ch = str[i]; // find the first different index
                for (int j = i+1; j < n; j++) 
                { 
                	if (str[i] == str[j]) puts("NO"), return;
                }
            }
        }
        puts("YES");
    }
    
    int main()
    { 
        ios_base::sync_with_stdio(false);
        cin.tie(nullptr); cout.tie(nullptr);
        int T; cin >> T;
        while (T--) 
            solve();
        return 0;
    }

# b #

1到n共有多少**位数都相同**的数

位数相同的数 1 2 3…9, 11, 22…111…11111…

暴力，肯定是不行的  
虽然是div3，否则还不如给大家布置c++课后作业？

#include<bits/stdc++.h>
    #define ll long long
    using namespace std;
    
    ll fun (int a, int b)
    { 
    	ll ans = 0;
    	int cnt = 1;
    	for (int i = 1; i <= a; ++i){ 
    		ans += cnt * b;
    		cnt *= 10;
    	}
    	return ans;
    }
    
    void solve()
    { 
        ll n, ans = 0; cin >> n;
        for (int i = 1; i <= 9; ++i) 
        	for (int j = 1; j <= 9; ++j) 
        		if (fun(i , j) <= n) ans++;
        		
        cout << ans << endl;
    }
    
    int main()
    { 
        ios_base::sync_with_stdio(false);
        cin.tie(nullptr); cout.tie(nullptr);
        int T; cin >> T;
        while (T--)
            solve();
        return 0;
    }

或者可以打表

int paiduan(int n)
    { 
        int count=0;
        if(n<10)return n;
        else if(n<=100)
        { 
            n=n/11;
            return 9+n;
        }
        else if(n<=1000)
        { 
            n=n/111;
            return 18+n;
        }
        else if(n<=10000)
        { 
            n=n/1111;
            return 27+n;
        }
        else if(n<=100000)
        { 
            n=n/11111;
            return 36+n;
        }
        else if(n<=1000000)
        { 
            n=n/111111;
            return 45+n;
        }
        else if(n<=10000000)
        { 
            n=n/1111111;
            return 54+n;
        }
        else if(n<=100000000)
        { 
            n=n/11111111;
            return 63+n;
        }
        else
        { 
            n=n/111111111;
            return 72+n;
        }
    }

# c #

输入一个数n  
上下左右四个值相差大于1

#include<bits/stdc++.h>
    using namespace std;
    
    void solve()
    { 
        int n; cin >> n;
        if (n == 2) { 
            cout << "-1\n";
        } else { 
            for (int i = 1; i <= n * n; i += 2) { 
                 cout << i << ' ';
                 if ((i + 1) % n == 0) cout << endl;
            }
            for (int i = 2; i <= n * n; i += 2) { 
                 cout << i << ' ';
                 if ((i + 1) % n == 0) cout << endl;
            }
               
        }
    }
    
    int main()
    { 
        ios_base::sync_with_stdio(false);
        cin.tie(nullptr); cout.tie(nullptr);
        int T; cin >> T;
        while (T--)
            solve();
        return 0;
    }

[https_codeforc.es_contest_1520]: https://codeforc.es/contest/1520