Leetcode 179. Largest Number

Given a list of non negative integers, arrange them such that they form the largest number.

Example 1:

Input: [10,2]
Output: “210”
Example 2:

Input: [3,30,34,5,9]
Output: “9534330”
Note: The result may be very large, so you need to return a string instead of an integer.

本题比较类似于基数排序的第一步，当首位相同时，我们不需要从第二位开始逐位比较

class Comp
{
public:
    bool operator()(const string& s1,const string& s2)
    {
        return s1+s2 > s2+s1;
    }
};

class Solution {
public:
    string largestNumber(vector<int>& nums) {
          vector<string> strs;
        for(int num:nums)
        {
            strs.push_back(to_string(num));
        }
        sort(strs.begin(),strs.end(),Comp());
        string res;
        if(strs[0][0]=='0') return "0";
        for(string& s:strs)
            res+=s;
        return res;
    }
};

转化为string之后，直接相加比较两个字符串谁打谁小。

summary

1. 比较两个数字字符串谁大谁小的办法