Largest Number

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.

先考虑字符串的长短

class Solution {
    string itoa(int num) {
        stringstream stream;
        stream << num;
        return stream.str();
    }
    
    static bool comp(const string& str1, const string& str2) {
        if(str1.size() > str2.size() || str2.empty()) return !comp(str2, str1);
        
        if(str1.empty()) {
            return !str2.empty();
        }
        
        int i = 0;
        while( i < str1.size() ) {
            if(str1[i] > str2[i]) return true;
            if(str1[i] < str2[i]) return false;
            i++;
        }
        string str2_next = i== str2.size() ? "" : str2.substr(i);
        return comp(str1, str2_next);
        return false;
    }
    
public:
    string largestNumber(vector<int>& nums) {
        vector<string> rst;
        for( int num : nums ) {
            rst.push_back(itoa(num));
        }
        sort(rst.begin(), rst.end(), comp);
        
        string str;
        for( string s : rst ) {
            str.append(s);
        }
        int i = 0;
        while( i < str.size() && str[i] == '0') i++;
        return i == str.size() ? "0" : str.substr(i);
    }
};