Codeforces Round #690 (Div. 3) ABC题代码

我比较菜，只能做得出ABC，大佬勿喷
比赛链接：https://codeforces.com/contest/1462

A. Favorite Sequence

模拟即可

#include 
using namespace std;
typedef long long ll;
int res[512];
int nums[512];

int main() {
     
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	int T;
    cin >> T;
    while(T--){
     
        int n;
        cin >> n;
        for(int i = 0;i<n;++i){
     
            cin >> nums[i];
        }
        int j = 0;
        for(int i = 0;i<n/2;++i){
     
            res[j++] = nums[i];
            res[j++] = nums[n - i - 1];
        }
        if(n % 2){
     
            res[j++] = nums[n/2];
        }else{
     
            res[j++] = nums[n/2];
            res[j++] = nums[n/2 + 1];
        }
        for(int i = 0;i<n;++i){
     
            cout << res[i] << " \n"[i == n-1];
        }
        // cout << endl;
    }
	return 0;
}

B. Last Year’s Substring

分类讨论，只要左右两边能凑2020就行了

#include 
using namespace std;
typedef long long ll;

int main() {
     
	// ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	int T,n;
    string s;
    cin >> T;
    while(T--){
     
        cin >> n;
        cin >> s;
        if(s[0] == '2'){
     
            if(s[1] == '0'){
     
                if(s[2] == '2'){
     
                    if(s[3] == '0' || s[n-1] == '0'){
     
                        cout << "YES" << endl;
                        continue;
                    }
                }else{
     
                    if(s.substr(n-2,2) == "20"){
     
                        cout << "YES" << endl;
                        continue;
                    }
                }
            }else{
     
                if(s.substr(n-3,3) == "020"){
     
                    cout << "YES" << endl;
                    continue;
                }
            }
        }else{
     
            if(s.substr(n-4,4) == "2020"){
     
                cout << "YES" << endl;
                continue;
            }
        }
        
        cout << "NO" << endl;
    }
	return 0;
}

C. Unique Number

菜鸡只会枚举

#include 
using namespace std;
typedef long long ll;
int res[] = {
     
    0,1,2,3,4,5,6,7,8,9,19,29,39,49,59,69,79,89,189,289,389,489,
    589,689,789,1789,2789,3789,4789,5789,6789,16789,26789,36789,46789,56789,156789,
    256789,356789,456789,1456789,2456789,3456789,13456789,23456789,123456789};

int main() {
     
	ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
	int T;
    cin >> T;
    while(T--){
     
        int n;
        cin >> n;
        if(n > 45){
     
            cout << "-1" << endl;
        }else{
     
            cout << res[n] << endl;
        }
    }
	return 0;
}