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.

 

C++代码实现：

#include<iostream>

#include<string>

#include<vector>

using namespace std;



class Solution {

public:

    string largestNumber(vector<int> &num) {

        if(num.empty())

            return "";

        string ret;

        int i,j;

        while(!num.empty())

        {

            i=0;

            for(j=1;j<(int)num.size();j++)

            {

                if((to_string(num[i])+to_string(num[j]))<(to_string(num[j])+to_string(num[i])))

                    i=j;

            }

            ret+=to_string(num[i]);

            num.erase(num.begin()+i);

        }

        while(ret.size()>1&&ret[0]=='0')

            ret.erase(ret.begin());

        return ret;

    }

};



int main()

{

    Solution s;

    vector<int> vec={3,30,34,5,9};

    cout<<s.largestNumber(vec)<<endl;

}

 

直接调用STL算法进行排序：

#include<iostream>

#include<vector>

#include<string>

#include<algorithm>

using namespace std;

//不能声明non-static成员函数

bool Mycmp(int n1,int n2)

{

    string s1=to_string(n1);

    string s2=to_string(n2);

    return s1+s2>s2+s1;

}

class Solution

{

public:

    string largestNumber(vector<int> &num)

    {

        if(num.empty())

            return "";

        string ret="";

        sort(num.begin(),num.end(),Mycmp);

//sort(num.begin(),num.end(),[](int n1,int n2){ return to_string(n1)+to_string(n2)>to_string(n2)+to_string(n1);});

        if(num[0]==0)

            return "0";

        for(auto a:num)

            ret+=to_string(a);

        return ret;

    }
//声明为static成员是可以的

static bool Mycmp(int n1,int n2)

{

    string s1=to_string(n1);

    string s2=to_string(n2);

    return s1+s2>s2+s1;

}

}; 
int main() 
{ 
　　Solution s; 
　　vector<int> num= {3,32,321}; 
　　cout<<s.largestNumber(num)<<endl; 
}