[CareerCup][Google Interview] 构造最大数

Given an array of elements find the largest possible number that can 

be formed by using the elements of the array. 
eg: 10 9 
ans: 910 
2 3 5 78 
ans: 78532 
100 9 
ans: 9100

http://www.careercup.com/question?id=9334650

把字符串排个序，比较方法是循环比较各个字符，如果对应位的字符大于另一个字符串的对应位则返回true，否则false。思想就是类似于要把尽可能大的数位放在更高位。

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

bool comp(const string &lhs, const string &rhs)
{
    int len = max(lhs.size(), rhs.size());

    for(int i = 0; i < len; i++)
    {
        int lIndex = i % lhs.size();
        int rIndex = i % rhs.size();
        if (lhs[lIndex] > rhs[rIndex])
            return true;
        else if (lhs[lIndex] < rhs[rIndex])
            return false;
    }

    return true;
}

string solve(vector<string> &a)
{
    sort(a.begin(), a.end(), comp);

    string s;

    for(int i = 0; i < a.size(); i++)
        s = s + a[i];

    return s;
}

int main()
{
    vector<string> a;
    a.push_back("10");
    a.push_back("9");
    cout << solve(a) << endl;

    vector<string> b;
    b.push_back("2");
    b.push_back("3");
    b.push_back("5");
    b.push_back("78");
    cout << solve(b) << endl;

    vector<string> c;
    c.push_back("100");
    c.push_back("9");
    cout << solve(c) << endl;
}