Program to create largest lexicographic number from a list of numbers in C++

Suppose we have a list of numbers called nums, we have to rearrange its order to form the largest possible number and return that as a string.

So, if the input is like nums = [20, 8, 85, 316], then the output will be "88531620".

To solve this, we will follow these steps −

• Define an array temp
• for each item i in nums:
  • insert i into temp as string
• sort the array temp based on lexicographic sequence (check for two strings a, b when a concatenate b is larger than b concatenate a or not)
• for each string s in temp:
  • res := res concatenate s
• return res

Let us see the following implementation to get better understanding −

Example

#include <bits/stdc++.h>
using namespace std;

static bool cmp(string a, string b) {
   return (a + b) >= (b + a);
}
string solve(vector<int>& nums) {
   vector<string> temp;
   for (int i : nums) {
      temp.push_back(to_string(i));
   }
   sort(temp.begin(), temp.end(), cmp);
   string res;
   for (string s : temp) {
      res += s;
   }
   return res;
}

int main(){
   vector<int> v = {20, 8, 85, 316};
   cout << solve(v);
}

Input

{20, 8, 85, 316}

Output

88531620