LeetCode 题解（134）: Largest Number

题目：

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.

题解：

自写comparator用于排序： str(a) + str(b) > str(b) + str(a)。注意结果连续个零的情况，只需返回一个0。Java需要高级语言操作，以后学来了再补上。

C++版：

class Solution {
public:
    string largestNumber(vector<int>& nums) {
        if(nums.size() == 0)
            return "";
            
        sort(nums.begin(), nums.end(), compare);
        string result = to_string(nums[0]);
        for(int i = 1; i < nums.size(); i++) {
            result += to_string(nums[i]);
        }
        
        if(result[0] == '0')
            return "0";
        return result;
    }
    
    static bool compare(int a, int b) {
        return to_string(a) + to_string(b) > to_string(b) + to_string(a);
    }
};

Python版：

class Solution:
    # @param {integer[]} nums
    # @return {string}
    def largestNumber(self, nums):
        strings = sorted([str(i) for i in nums], cmp = self.compare)
        result = "".join(strings).lstrip('0')
        return result or '0'
        
    def compare(self, a, b):
        return [1, -1][a + b > b + a]