样例对了啊！

#include <iostream>
#include <cctype>
#include <cstdio>
#include <algorithm>
#include <string>
using namespace std;

class Node
{
	public:
		int f, x;
		Node();
};

Node::Node()
{
	x = 0;
}

inline bool cmp(const Node& x, const Node& y)
{
	return (x.f == y.f ? x.f < y.f : x.x > y.x);
}

Node a[30];

int main()
{
	ios::sync_with_stdio(false);
	int n, cur = 0;
	cin >> n;
	getchar();
	for (register int i = 1; i <= n; i++)
	{
		string s;
		getline(cin, s);
		transform(s.begin(), s.end(), s.begin(), ::toupper);
		int len = s.length() - 1;
		for (register int j = 0; j <= len; j++)
		{
			if (isalpha(s[j]))
			{
				a[s[j] - 'A' + 1].x++;
				a[s[j] - 'A' + 1].f = s[j];
			}
		}
	}
	sort(a + 1, a + 30, cmp);
	for (register int i = 1; i <= 26; i++)
	{
		if (a[i].x == 0)
		{
			continue;
		}
		else
		{
			cout << char(a[i].f) << " " << a[i].x << endl;
		}
	}
	system("pause");
	return 0;
}