Arrange an Array into the Smallest Number

1. Problem Description

Given an array of positive integers, concatenate all numbers to form one number and print the smallest possible result. For example, for {3,32,321}, the smallest number that can be formed is 321323.

2. Approach

• Custom string ordering

3. Implementation

package main

import (
	"sort"
	"strconv"
)

/**
 * The class name, method name, and parameter names in the code have already been specified. Do not modify them; directly return the value required by the method.
 *
 * @param numbers one-dimensional int array
 * @return string
 */
// Time complexity: O(NlogN), using sorting
// Space complexity: O(1)
func PrintMinNumber(numbers []int) string {
	sort.Slice(numbers, func(i, j int) bool {
		a, b := strconv.Itoa(numbers[i]), strconv.Itoa(numbers[j])
		return a+b < b+a
	})
	res := ""
	for _, number := range numbers {
		res += strconv.Itoa(number)
	}
	return res
}

func minNumber(nums []int) string {
    strs := make([]string, 0 , len(nums))
    for _, num := range nums {
        str := strconv.Itoa(num)
        strs = append(strs, str)
    }
    sort.Slice(strs, func(i,j int) bool {
        a := strs[i]+ strs[j]
        b := strs[j]+ strs[i]
        return a < b 
    })
    res := ""
    for _, str := range strs{
        res += str
    }
    return res
}

4. References

• Arrange an Array into the Smallest Number - NowCoder
• Sword Offer 45. Arrange an Array into the Smallest Number - LeetCode