feat: solve No.1704

Author: BaffinLee

1701-1800/1704. Determine if String Halves Are Alike.md

@@ -0,0 +1,83 @@
+# 1704. Determine if String Halves Are Alike
+
+- Difficulty: Easy.
+- Related Topics: String, Counting.
+- Similar Questions: .
+
+## Problem
+
+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.
+```
+
+ 
+**Constraints:**
+
+
+	
+- `2 <= s.length <= 1000`
+	
+- `s.length` is even.
+	
+- `s` consists of **uppercase and lowercase** letters.
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var halvesAreAlike = function(s) {
+    var map = {
+        a: true,
+        e: true,
+        i: true,
+        o: true,
+        u: true,
+        A: true,
+        E: true,
+        I: true,
+        O: true,
+        U: true,
+    };
+    var half = s.length / 2;
+    var count = 0;
+    for (var i = 0; i < half; i++) {
+        if (map[s[i]]) count++;
+        if (map[s[i + half]]) count--;
+    }
+    return count === 0;
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1).