Uva 10008 - What's Cryptanalysis?

#include<bits/stdc++.h>

using namespace std;

struct Ch{

char cha;

int digit;

}ch[31];

bool cmp(Ch a, Ch b) {

return (a.digit > b.digit);

}

int main()

{

int k,l,j,i,m,n;

string s,s1;

char s2[101];

for( i = 0 ; i < 31 ; i++ )	ch[i].digit=0,ch[i].cha=(char)(i+65);

cin >> n;

cin.getline(s2,0);

while(n--){

cin.getline(s2,101);

s = s2;

transform(s.begin(), s.end(), s.begin(), ::toupper);

for( i = 0 ; i < s.size()  ; i++ ) {

if(s[i]>='A' && s[i]<='Z')

ch[s[i]-'A'].digit++;

}

}

stable_sort(ch,ch+26,cmp);

for ( i = 0 ;  i < 31  &&  ch[i].digit > 0 ;  i++ )

printf("%c %d\n",ch[i].cha,ch[i].digit);

return 0;

}