Largest Number (LeetCode)

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

Note: The result may be very large, so you need to return a string instead of an integer.

Example 1:
Input: nums = [10,2]
Output: "210"

Example 2:
Input: nums = [3,30,34,5,9]
Output: "9534330"

Example 3:
Input: nums = [1]
Output: "1"

Example 4:
Input: nums = [10]
Output: "10"

Constraints:

  • 1 <= nums.length <= 100
  • 0 <= nums[i] <= 10^9

For original task refer to leetcode

Approach

  • First convert given array of integer values to array of string values
  • Next sort the values by their alphanumeric values in a combination where:
    • b + a and a + b are compared
    • here b + a refers to b-string concatenated with a-string
    • a and b refers to string values in the array

Time Complexity: O(N log(N)), where N is the number of elements in the array.

Space Complexity: O(1), only operational variables are used.

Solution (Java)

class Solution {
    public String largestNumber(int[] nums) {
        String[] strs = new String[nums.length];
        for (int i = 0; i < nums.length; i++) {
            strs[i] = Integer.toString(nums[i]);
        }
        Arrays.sort(strs, (a, b) -> (b + a).compareTo(a + b));
        
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < nums.length; i++) {
            sb.append(strs[i]);
        }
        
        String result = sb.toString();
        return result.startsWith("0") ? "0" : result;
    }
}