problem: (D) Minimum number of steps Solution In C/C++ Archive

#include<bits/stdc++.h> using namespace std; int c,d,i,n,m,k,x,j=1000000007; string s; main(){ cin>>s; for(i=s.size()-1;i>=0;i–){ if(s==’b’)c++;else{ k+=c;c*=2;k%=j;c%=j; } } cout<<k; }