Problem:
Score : 600 points

Problem Statement

You are given a string s consisting of A, B and C.

Snuke wants to perform the following operation on s as many times as possible:

Choose a contiguous substring of s that reads ABC and replace it with BCA.

Find the maximum possible number of operations.

Constraints

1 \leq |s| \leq 200000

Each character of s is A, B and C.

Input

Input is given from Standard Input in the following format:

s

Output

Find the maximum possible number of operations.

Sample Input 1

ABCABC

Sample Output 1

3

You can perform the operations three times as follows: ABCABC → BCAABC → BCABCA → BCBCAA. This is the maximum result.

Sample Input 2

C

Sample Output 2

0

Sample Input 3

ABCACCBABCBCAABCB

Sample Output 3

6

Solution in C++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

int main()
{   int ans = 0;
    string s;
    cin >> s;
    vector <int> v;
    for(int i = 0; i < s.size(); i++){
        if(s[i] == 'B' && s[i+1] == 'C' && i + 1 < s.size()){
            v.push_back('D');
            i++;
            continue;
        }
        v.push_back(s[i]);
    }
    int m = 5000;
    while(m--){
        int cnt = 0;
        for(int i  =0; i < max((int)v.size() - 1 , 0); i++){
            if(v[i] == 'A' && v[i+1] == 'D'){
                v[i] = 'D'; v[i+1] = 'A';
                ans++;
            }
        }
        for(int i  =0; i < max((int)v.size() - 1 , 0); i++){
            if(v[i] == 'A' && v[i+1] == 'D'){
                cnt++;
                break;
            }
        }
        if(cnt==0){
            break;
        }
    }
    cout << ans << '\n';
}