0179. Largest Number

https://leetcode.com/problems/largest-number

Description

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] <= 109

ac

// soooo smart!
// key: sort array -> comparator -> given two element, how to decide their order.

class Solution {
    public String largestNumber(int[] nums) {
        // edge cases
        if (nums.length == 0) return null;
        if (nums.length == 1) return String.valueOf(nums[0]);

        // int[] -> String[]
        String[] strs = new String[nums.length];
        for (int i = 0; i < nums.length; i++) {
            strs[i] = String.valueOf(nums[i]);
        }

        // sort, recursively
        Arrays.sort(strs, (String s1, String s2) -> {
            String n1 = s1 + s2;
            String n2 = s2 + s1;
            return n1.compareTo(n2);
        });

        // edge case: all 0
        if (strs[strs.length - 1].equals("0")) return "0";

        // append
        StringBuilder sb = new StringBuilder();
        for (int i = strs.length - 1; i >= 0; i--) {
            sb.append(strs[i]);
        }

        //return
        return sb.toString();
    }
}