1903. Largest Odd Number in String

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.

Related Topics:
Greedy

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) {
        int i = s.size() - 1;
        while (i >= 0 && (s[i] - '0') % 2 == 0) --i;
        return s.substr(0, i + 1);
    }
};