C - abc285_brutmhyhiizp

C - abc285_brutmhyhiizp

https://atcoder.jp/contests/abc285/tasks/abc285_c

思路

对于长度为L+1的字符序列， A[1], ..., A[L]， A[L+1]

首先统计长度为1 到 L 字符序列 总数， 即

A , ... , Z

AA, AB, ..., ZZ

AAA, ..., ZZZ

....

 

然后统计 A[1], ..., A[L]， A[L+1] 的序数

A...A ---- L+1 个A

到

A[1], ..., A[L]， A[L+1]

 

Code

https://atcoder.jp/contests/abc285/submissions/38071836

string s;
 
int main()
{
    cin >> s;
 
    int size = s.size();
    long long last_order = 0;
    for(int i=0; i<size; i++){
        char a = s[i];
        int ai = a - 'A';
        last_order *= 26;
        last_order += ai;
    }
 
    long long last_count = last_order + 1;
 
    long long all_count = 0;
    all_count = last_count;
    
    int slen = s.size();
    long long level_power = 1;
    long long prev_count = 0;
    for(int i=1; i<slen; i++){
        level_power *= 26;
        prev_count += level_power;
    }
    
    all_count += prev_count;
    
    cout << all_count << endl;
 
    return 0;
}