1556. Thousand Separator.md

1556. Thousand Separator

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the first one in Biweekly Contest 33.

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Difficulty : Easy

Related Topics : String

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Given an integer n, add a dot (".") as the thousands separator and return it in string format.

Example 1:

Input: n = 987
Output: "987"

Example 2:

Input: n = 1234
Output: "1.234"

Example 3:

Input: n = 123456789
Output: "123.456.789"

Example 4:

Input: n = 0
Output: "0"

Constraints:

• 0 <= n < 2^31

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Solution

• mine
  • Java
    • Runtime: 0 ms, faster than 100.00%, Memory Usage: 37 MB, less than 83.92% of Java online submissions

      // O(N)time
      // O(N)space
      public String thousandSeparator(int n) {
          if(n == 0) return "0";
          LinkedList<Object> list = new LinkedList<>();
          int count = 0;
          while(n > 0){
              if(count==3){
                  list.addFirst(".");
                  count = 0;
              }
              count++;
              list.addFirst(n % 10);
              n /= 10;
          }
          StringBuilder res = new StringBuilder();
          while(!list.isEmpty()){
              res.append(list.removeFirst());
          }
          return res.toString();
      }
      

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