179. Largest Number

Largest Number




https://leetcode.com/problems/largest-number/discuss/53158/My-Java-Solution-to-share


https://www.javatpoint.com/java-string-compareto


https://en.wikipedia.org/wiki/Lexicographical_order



https://leetcode.com/problems/largest-number/discuss/53158/My-Java-Solution-to-share


For example, using the natural order of the integers, the lexicographical ordering on the subsets of three elements of S = {1, 2, 3, 4, 5, 6} is
123 < 124 < 125 < 126 < 134 < 135 < 136 < 145 < 146 < 156 <
234 < 235 < 236 < 245 < 246 < 256 < 345 < 346 < 356 < 456.





The idea here is basically implement a String comparator to decide which String should come first during concatenation. Because when you have 2 numbers (let's convert them into String), you'll face only 2 cases:
For example:

String s1 = "9";
String s2 = "31";

String case1 =  s1 + s2; // 931
String case2 = s2 + s1; // 319


Apparently, case1 is greater than case2 in terms of value.
So, we should always put s1 in front of s2.










class Solution {
    public String largestNumber(int[] num) {
      if(num == null ||num.length == 0){
        return "";
      }
      
      // convert int array to string array, so we can concatenate. otherwise, if we still use int, combine two int, would 
// say combine 57, 26, its gonna be 56 * 100 + 26 , 

      String[] strArray = new String[num.length];
      for(int i = 0; i < num.length; i++){
        strArray[i] = String.valueOf(num[i]); // String.valueOf
      }
      
      // comparator fo decide which string should come first in concatenation
      Arrays.sort(strArray, new Comparator<String>(){
        @Override
        public int compare (String str1, String str2){
          String s1 = str1 + str2;
          String s2 = str2 + str1;
          return s2.compareTo(s1); // reverse order
          
        }
      });
      
      // an extrmem case when you have bunch of 0s in the int array
      if(strArray[0].charAt(0) == '0'){
        return "0";
      }
      
      StringBuilder sb = new StringBuilder();
      for(String s : strArray){
        sb.append(s);
      }
      
      return sb.toString();
    }
}

class Solution {
    public String largestNumber(int[] nums) {
        ArrayList<String> list = new ArrayList<>();
        for (int i = 0; i < nums.length; i++)
            list.add(Integer.toString(nums[i]));
        Collections.sort(list,(a,b) -> (int)(Long.parseLong(b+a) - Long.parseLong(a+b)) );
        StringBuilder sb = new StringBuilder();
        for(String x:list) {
            sb.append(x);
        }
        //remove leading 0
        return sb.toString().replaceFirst("^0+(?!$)", "");
    }
}

 

class Solution {
    public String largestNumber(int[] nums) {
        ArrayList<String> list = new ArrayList<>();
        for (int i = 0; i < nums.length; i++)
            list.add(Integer.toString(nums[i]));
        Collections.sort(list,(a,b) -> Integer.valueOf(b+a) - Integer.valueOf(a+b));
        StringBuilder sb = new StringBuilder();
        for(String x:list) {
            sb.append(x);
        }
        //remove leading 0
        return sb.toString().replaceFirst("^0+(?!$)", "");
    }
}

 

 

Given a list of non negative integers, arrange them such that they form the largest number.

Example 1:

Input: [10,2]
Output: "210"

Example 2:

Input: [3,30,34,5,9]
Output: "9534330"