UVa 10062 Tell me the frequencies!

Code：

#include<stdio.h>

#include<stdlib.h>

#include<iostream>

#include<algorithm>

#include<math.h>

#include<map>

#include<vector>

using namespace std;

struct ic

{

    char ch;

    int n;

    ic(int a,char b):n(a),ch(b){};

    friend bool operator < (ic a,ic b);

};

bool operator < (ic a,ic b)

{

    if(a.n<b.n) return true;

    else if(a.n==b.n)

    {

        if(a.ch>=b.ch) return true;

    }

    return false;

}

int main()

{

    string str;

    bool first=0;

    while(getline(cin,str))

    {

        if(first) cout<<endl;

        map<char,int> m;

        vector<ic> v;

        int len=str.size();

        for(int i=0;i<len;i++)

        {

            m[str[i]]+=1;

        }

        for(auto it=m.begin();it!=m.end();it++)

        {

            v.push_back(ic(it->second,it->first));

        }

        sort(v.begin(),v.end());

        int vlen=v.size();

        for(int i=0;i<vlen;i++)

        {

             printf("%d %d\n",v[i].ch,v[i].n);

        }

        first=1;

    }

    return 0;

}