1903

1903. Largest Odd Number in String (Easy)

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 <= 105
• num only consists of digits and does not contain any leading zeros.

Companies: Amazon, Adobe

Related Topics:
Math, String, Greedy

Similar Questions:

• Largest 3-Same-Digit Number in String (Easy)

Hints:

• In what order should you iterate through the digits?
• If an odd number exists, where must the number start from?

Solution 1. Find the rightmost odd number

// OJ: https://leetcode.com/problems/largest-odd-number-in-string/
// Author: github.com/lzl124631x
// Time: O(N)
// Space: O(1)
class Solution {
public:
    string largestOddNumber(string s) {
        while (s.size() && (s.back() - '0') % 2 == 0) s.pop_back();
        return s;
    }
};