【topcoder】 SRM 144 div 2 200

Problem
Problem Statement
Computers tend to store dates and times as single numbers which represent the number of seconds or milliseconds since a particular date. Your task in this problem is to write a method whatTime, which takes an int, seconds, representing the number of seconds since midnight on some day, and returns a string formatted as “< H >:< M >:< S >”. Here, < H > represents the number of complete hours since midnight, < M > represents the number of complete minutes since the last complete hour ended, and < S > represents the number of seconds since the last complete minute ended. Each of < H >, < M >, and < S > should be an integer, with no extra leading 0’s. Thus, if seconds is 0, you should return “0:0:0”, while if seconds is 3661, you should return “1:1:1”. Definition
Class:
Time
Method:
whatTime
Parameters:
int
Returns:
string
Method signature:
string whatTime(int seconds) (be sure your method is public)
Limits
Time limit (s):
2.000
Memory limit (MB):
64
Constraints
seconds will be between 0 and 24*60*60 - 1 = 86399, inclusive.
Examples
0)
0 Returns: “0:0:0”
1)
3661 Returns: “1:1:1”
2)
5436 Returns: “1:30:36”
3)
86399 Returns: “23:59:59”
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Solution
Get 155.57/200 points

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

class Time{
    public:
        string whatTime(int seconds);

};

string Time::whatTime(int seconds){
    int h = seconds / 60 / 60;
    int m = seconds / 60 - h*60;
    int s = seconds - h*60*60 - m*60;
    stringstream ss;
    string str, str2, str3;
    ss << h;
    ss >> str;
    ss.clear();
    ss << m;
    ss >> str2;
    ss.clear();
    ss << s;
    ss >> str3;
    return str + ":" + str2 + ":" + str3;
}