##### Welcome to Subscribe On Youtube

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

# 1903. Largest Odd Number in String

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.

• 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 '';
}