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Formatted question description: https://leetcode.ca/all/1903.html

1903. Largest Odd Number in String

Level

Easy

Description

You are given a string num, representing a large integer. Return the largest-valued odd integer (as a string) that is a non-empty substring of num, or an empty string "" if no odd integer exists.

A substring is a contiguous sequence of characters within a string.

Example 1:

Input: num = “52”

Output: “5”

Explanation: The only non-empty substrings are “5”, “2”, and “52”. “5” is the only odd number.

Example 2:

Input: num = “4206”

Output: “”

Explanation: There are no odd numbers in “4206”.

Example 3:

Input: num = “35427”

Output: “35427”

Explanation: “35427” is already an odd number.

Constraints:

• 1 <= num.length <= 10^5
• num only consists of digits and does not contain any leading zeros.

Solution

Any number that ends with an odd digit is an odd number. If a digit in num is an odd number, then the substring from index 0 to the current digit is ghe largest odd number that ends with the digit. Therefore, find the rightmost odd digit in nums, and return the substring from index 0 to the rightmost odd digit.

• Java
• C++
• Python
• Go
• Javascript
• TypeScript

• class Solution {
      public String largestOddNumber(String num) {
          for (int i = num.length() - 1; i >= 0; i--) {
              char c = num.charAt(i);
              int digit = c - '0';
              if (digit % 2 != 0)
                  return num.substring(0, i + 1);
          }
          return "";
      }
  }
  
  ############
  
  class Solution {
      public String largestOddNumber(String num) {
          for (int i = num.length() - 1; i >= 0; --i) {
              int c = num.charAt(i) - '0';
              if ((c & 1) == 1) {
                  return num.substring(0, i + 1);
              }
          }
          return "";
      }
  }
  

• // OJ: https://leetcode.com/problems/largest-odd-number-in-string/
  // Time: O(N)
  // Space: O(1)
  class Solution {
  public:
      string largestOddNumber(string s) {
          int i = s.size() - 1;
          while (i >= 0 && (s[i] - '0') % 2 == 0) --i;
          return s.substr(0, i + 1);
      }
  };
  

• class Solution:
      def largestOddNumber(self, num: str) -> str:
          for i in range(len(num) - 1, -1, -1):
              if (int(num[i]) & 1) == 1:
                  return num[: i + 1]
          return ''
  
  ############
  
  # 1903. Largest Odd Number in String
  # https://leetcode.com/problems/largest-odd-number-in-string/
  
  class Solution:
      def largestOddNumber(self, nums: str) -> str:
          res = None
          
          for i,x in enumerate(nums):
              if int(x) & 1:
                  res = nums[:i + 1]
          
          return "" if not res else res
  
  

• func largestOddNumber(num string) string {
  	for i := len(num) - 1; i >= 0; i-- {
  		c := num[i] - '0'
  		if (c & 1) == 1 {
  			return num[:i+1]
  		}
  	}
  	return ""
  }
  

• /**
   * @param {string} num
   * @return {string}
   */
  var largestOddNumber = function (num) {
      let n = num.length;
      for (let j = n - 1; j >= 0; j--) {
          if (num.charAt(j) & (1 == 1)) {
              return num.slice(0, j + 1);
          }
      }
      return '';
  };
  
  

• function largestOddNumber(num: string): string {
      for (let i = num.length - 1; ~i; --i) {
          if (Number(num[i]) & 1) {
              return num.slice(0, i + 1);
          }
      }
      return '';
  }
  
  

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