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.add(v + "");
        }
        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();
    }
}

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