algorithms/cpp/largestNumber/largestNumber.cpp

// Source : https://oj.leetcode.com/problems/largest-number/
// Author : Hao Chen
// Date   : 2015-01-16

/********************************************************************************** 
 * 
 * Given a list of non negative integers, arrange them such that they form the largest number.
 * 
 * For example, given [3, 30, 34, 5, 9], the largest formed number is 9534330.
 * 
 * Note: The result may be very large, so you need to return a string instead of an integer.
 * 
 * Credits:Special thanks to @ts for adding this problem and creating all test cases.
 *               
 **********************************************************************************/

class Solution {
    public:

        //compare function
        static bool comp (string& s1, string& s2) { return s1+s2 > s2+s1; }

        string largestNumber(vector<int> &num) {

            //convert int to string
            vector<string> v;
            for (int i=0; i<num.size(); i++) {
                v.push_back(to_string(num[i]));
            }

            //sort the string
            sort(v.begin(), v.end(), comp);

            //generate the result
            string result;
            for(int i=0; i<v.size(); i++ ){
                result+=v[i];
            }

            //special case: start with zero (e.g. [0, 0])
            if (result[0]=='0') return "0";

            return result;
        }
};