Leetcode题解(8):L179/Largest Number

L179: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.

解题思路：
其实可以分解为两个数字的比较排序
对于两个备选数字a和b，如果int(str(a) + str(b)) > int(str(b) + str(a))，则a在b之前，否则b在a之前
按此对其从大到小排序即可

class Solution {
public:
    //long(str(a) + str(b)) > long(str(b) + str(a))，则a在b之前
    static bool cmpStr(string &a, string &b) {
            string ab = a + b;
            string ba = b + a;
            return stol(ab) > stol(ba);
    }

    string largestNumber(vector<int>& nums) {
        int numsLen = nums.size();
        if (numsLen < 1) return "";
        if (numsLen == 1) return to_string(nums[0]);

        //转化为字符串数组,方便处理
        vector<string> strVec;
        for (int i = 0; i < numsLen; i++) {
            strVec.push_back(to_string(nums[i]));
        }

        //字符串排序
        sort(strVec.begin(), strVec.end(), cmpStr);

        //去掉开头的0
        int i = 0;
        while (i < numsLen && strVec[i] == "0") 
            i++;

        if (i == numsLen) return "0";

        //字符串拼接
        string rt = "";
        while(i < numsLen)
            rt += strVec[i++];

        return rt;
    }
};