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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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