# Question

Formatted question description: https://leetcode.ca/all/179.html

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

Since 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"


Constraints:

• 1 <= nums.length <= 100
• 0 <= nums[i] <= 109

# Algorithm

For two numbers a and b, if you convert them to strings, if ab> ba, then a will be ranked first,

• For example, 9 and 34, since 934>349, 9 is in front,
• For example, 30 and 3, because 303<330, 3 is in front of 30.

After sorting the original array according to this rule, converting each number into a string and then concatenating it is the final result.

# Code

• import java.util.Arrays;
import java.util.Comparator;

public class Largest_Number {
class Solution {

public String largestNumber(int[] nums) {
// Get input integers as strings.
String[] asStrs = new String[nums.length];
for (int i = 0; i < nums.length; i++) {
asStrs[i] = String.valueOf(nums[i]);
}

// Sort strings according to custom comparator.
Arrays.sort(asStrs, new LargerNumberComparator());

// If, after being sorted, the largest number is 0, the entire number
// is zero.
if (asStrs[0].equals("0")) {
return "0";
}

// Build largest number from sorted array.
String largestNumberStr = new String();
for (String numAsStr : asStrs) {
largestNumberStr += numAsStr;
}

return largestNumberStr;
}

private class LargerNumberComparator implements Comparator<String> {
@Override
public int compare(String a, String b) {
String order1 = a + b;
String order2 = b + a;
return order2.compareTo(order1);
}
}

}
}

############

class Solution {
public String largestNumber(int[] nums) {
List<String> vs = new ArrayList<>();
for (int v : nums) {
}
vs.sort((a, b) -> (b + a).compareTo(a + b));
if ("0".equals(vs.get(0))) {
return "0";
}
return String.join("", vs);
}
}

• // OJ: https://leetcode.com/problems/largest-number/
// Time: O(NlogN * W) where W is the max length of the number strings.
// Space: O(NW)
class Solution {
public:
string largestNumber(vector<int>& A) {
vector<string> v;
for (int n : A) v.push_back(to_string(n));
sort(begin(v), end(v), [](auto &a, auto &b) {
for (int i = 0; i < a.size() + b.size(); ++i) {
char x = i < a.size() ? a[i] : b[i - a.size()], y = i < b.size() ? b[i] : a[i - b.size()];
if (x != y) return x > y;
}
return false; // don't return true which will result in infinite loop
});
if (v[0] == "0") return "0";
string ans;
for (auto &s : v) ans += s;
return ans;
}
};

• class Solution:
def largestNumber(self, nums: List[int]) -> str:
nums = [str(v) for v in nums]
nums.sort(key=cmp_to_key(lambda a, b: 1 if a + b < b + a else -1))
return "0" if nums[0] == "0" else "".join(nums)

############

class Solution:
# @param {integer[]} nums
# @return {string}
def largestNumber(self, nums):
def cmpFunc(a, b):
stra, strb = str(a), str(b)
if stra + strb < strb + stra:
return -1
elif stra + strb > strb + stra:
return 1
else:
return 0

nums.sort(cmp=cmpFunc, reverse=True)
return "".join(str(num) for num in nums) if sum(nums) != 0 else "0"


• func largestNumber(nums []int) string {
vs := make([]string, len(nums))
for i, v := range nums {
vs[i] = strconv.Itoa(v)
}
sort.Slice(vs, func(i, j int) bool {
return vs[i]+vs[j] > vs[j]+vs[i]
})
if vs[0] == "0" {
return "0"
}
return strings.Join(vs, "")
}

• using System;
using System.Globalization;
using System.Collections.Generic;
using System.Linq;
using System.Text;

public class Comparer: IComparer<string>
{
public int Compare(string left, string right)
{
return Compare(left, right, 0, 0);
}

private int Compare(string left, string right, int lBegin, int rBegin)
{
var len = Math.Min(left.Length - lBegin, right.Length - rBegin);
for (var i = 0; i < len; ++i)
{
if (left[lBegin + i] != right[rBegin + i])
{
return left[lBegin + i] < right[rBegin + i] ? -1 : 1;
}
}

if (left.Length - lBegin == right.Length - rBegin)
{
return 0;
}
if (left.Length - lBegin > right.Length - rBegin)
{
return Compare(left, right, lBegin + len, rBegin);
}
else
{
return Compare(left, right, lBegin, rBegin + len);
}
}
}

public class Solution {
public string LargestNumber(int[] nums) {
var sb = new StringBuilder();
var strs = nums.Select(n => n.ToString(CultureInfo.InvariantCulture)).OrderByDescending(s => s, new Comparer());

var nonZeroOccurred = false;
foreach (var str in strs)
{
if (!nonZeroOccurred && str == "0") continue;
sb.Append(str);
nonZeroOccurred = true;
}
return sb.Length == 0 ? "0" : sb.ToString();
}
}