179. Largest Number 解题记录

题目描述：

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.

解题思路：

可以先把int数组转化为string数组,然后再写一个sort函数用的cmp函数,如果字符串a+b>b+a,则不变位置,否则换位置.用sort函数对数组进行排序,最后再把所有字符串相加.

代码：

class Solution {
public:
    string largestNumber(vector<int>& nums) {
        int n=nums.size();
        vector<string> str(n);
        for(int i=0;i<n;++i)
        //将int数组转换为字符串数组
        {
            str[i] = to_string(nums[i]);
        }
        sort(str.begin(), str.end(), cmp);  //排序
        string res = "";
        for(int i=0;i<n;i++)
        {
            res += str[i];
        }
        if(res[0]=='0')
        //如果开头是'0'就说明这个字符串全为'0'，只要返回"0"即可
            return "0";
        return res;

    }
    static bool cmp(string strnum1, string strnum2)
    {
        string str1 = strnum1+strnum2;
        string str2 = strnum2+strnum1;
        return str1>str2;
    }
};