Formatted question description: https://leetcode.ca/all/1704.html

# 1704. Determine if String Halves Are Alike (Easy)

You are given a string s of even length. Split this string into two halves of equal lengths, and let a be the first half and b be the second half.

Two strings are alike if they have the same number of vowels ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U'). Notice that s contains uppercase and lowercase letters.

Return true if a and b are alike. Otherwise, return false.

Example 1:

Input: s = "book"
Output: true
Explanation: a = "bo" and b = "ok". a has 1 vowel and b has 1 vowel. Therefore, they are alike.


Example 2:

Input: s = "textbook"
Output: false
Explanation: a = "text" and b = "book". a has 1 vowel whereas b has 2. Therefore, they are not alike.
Notice that the vowel o is counted twice.


Example 3:

Input: s = "MerryChristmas"
Output: false


Example 4:

Input: s = "AbCdEfGh"
Output: true


Constraints:

• 2 <= s.length <= 1000
• s.length is even.
• s consists of uppercase and lowercase letters.

Related Topics:
String

## Solution 1.

// OJ: https://leetcode.com/problems/determine-if-string-halves-are-alike/

// Time: O(N)
// Space: O(N)
class Solution {
int count(string s) {
int cnt = 0;
for (char c : s) {
c = tolower(c);
cnt += c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
return cnt;
}
public:
bool halvesAreAlike(string s) {
return count(s.substr(0, s.size() / 2)) == count(s.substr(s.size() / 2));
}
};


Or

// OJ: https://leetcode.com/problems/determine-if-string-halves-are-alike/

// Time: O(N)
// Space: O(1)
class Solution {
int count(string &s, int begin, int end) {
int cnt = 0;
for (int i = begin; i < end; ++i) {
char c = tolower(s[i]);
cnt += c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
return cnt;
}
public:
bool halvesAreAlike(string s) {
return count(s, 0, s.size() / 2) == count(s, s.size() / 2, s.size());
}
};


Java

class Solution {
public boolean halvesAreAlike(String s) {
s = s.toLowerCase();
int length = s.length();
int halfLength = length / 2;
int vowels1 = 0, vowels2 = 0;
for (int i = 0; i < halfLength; i++) {
char c1 = s.charAt(i), c2 = s.charAt(i + halfLength);
if (isVowel(c1))
vowels1++;
if (isVowel(c2))
vowels2++;
}
return vowels1 == vowels2;
}

public boolean isVowel(char c) {
return c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u';
}
}