115：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.

解析：这题可以先把每个整数变成字符串，得到一个字符串数组，然后把这个数组按特定规则排个序，顺序输出即可。
代码如下：

// 时间复杂度 O(nlogn)，空间复杂度 O(n)class Solution {public:        string largestNumber(vector<int>& nums) {                vector<string> tmp;                bool all_zero = true;                for (auto val : nums) {                        if (val != 0) all_zero = false;                        tmp.push_back(to_string(val));                }                if (all_zero) return "0"; // 考虑了输入全为 0 这种特殊情况                sort(tmp.begin(), tmp.end(), compare());//              sort(tmp.begin(), tmp.end(), [=](const string& s1, const string& s2){//                      return (s1 + s2) < (s2 + s1); });                string result;                for (int i = tmp.size() - 1; i >= 0; --i)                        result += tmp[i];                return result;        }private:        struct comapre() {                bool operator()(const string& s1, const string& s2) {                        return (s1 + s2) < (s2 + s1);                }        };};