Merge branch 'master' of github.com:BaffinLee/leetcode-javascript

Author: BaffinLee

1401-1500/1456. Maximum Number of Vowels in a Substring of Given Length.md

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+# 1456. Maximum Number of Vowels in a Substring of Given Length
+
+- Difficulty: Medium.
+- Related Topics: String, Sliding Window.
+- Similar Questions: Maximum White Tiles Covered by a Carpet, Minimum Recolors to Get K Consecutive Black Blocks, Length of the Longest Alphabetical Continuous Substring.
+
+## Problem
+
+Given a string `s` and an integer `k`, return **the maximum number of vowel letters in any substring of **`s`** with length **`k`.
+
+**Vowel letters** in English are `'a'`, `'e'`, `'i'`, `'o'`, and `'u'`.
+
+ 
+Example 1:
+
+```
+Input: s = "abciiidef", k = 3
+Output: 3
+Explanation: The substring "iii" contains 3 vowel letters.
+```
+
+Example 2:
+
+```
+Input: s = "aeiou", k = 2
+Output: 2
+Explanation: Any substring of length 2 contains 2 vowels.
+```
+
+Example 3:
+
+```
+Input: s = "leetcode", k = 3
+Output: 2
+Explanation: "lee", "eet" and "ode" contain 2 vowels.
+```
+
+ 
+**Constraints:**
+
+
+	
+- `1 <= s.length <= 105`
+	
+- `s` consists of lowercase English letters.
+	
+- `1 <= k <= s.length`
+
+
+
+## Solution
+
+```javascript
+/**
+ * @param {string} s
+ * @param {number} k
+ * @return {number}
+ */
+var maxVowels = function(s, k) {
+    var i = 0;
+    var j = 0;
+    var count = isVowel(s, j) ? 1 : 0;
+    var max = count;
+    while (j < s.length - 1) {
+        j++;
+        count += (isVowel(s, j) ? 1 : 0);
+        if (j - i > k - 1) {
+            count -= (isVowel(s, i) ? 1 : 0);
+            i++;
+        }
+        max = Math.max(max, count);
+    }
+    return max;
+};
+
+var isVowel = function(s, i) {
+    return ['a', 'e', 'i', 'o', 'u'].includes(s[i]);
+};
+```
+
+**Explain:**
+
+nope.
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1).