Time: 14 ms (31.71%) Space: 59 MB (19.51%)

Author: pertrai1

0340-longest-substring-with-at-most-k-distinct-characters/longest-substring-with-at-most-k-distinct-characters.ts

@@ -0,0 +1,36 @@
+/**
+ * @time - O(n) where n is the length of s
+ *          (each character visited at most twice by sliding window pointers)
+ * @space - O(k) where k is the maximum number of distinct characters allowed;
+ *          the map stores at most k + 1 characters at any time before shrinking
+ */
+function lengthOfLongestSubstringKDistinct(s: string, k: number): number {
+    if (k === 0) return 0;
+
+    const characterCount = new Map<string, number>();
+    let left = 0;
+    let maxLength = 0;
+
+    // Expand the window by moving the right pointer
+    for (let right = 0; right < s.length; right++) {
+        const char = s[right];
+        // Add current character to frequency map
+        characterCount.set(char, (characterCount.get(char) || 0) + 1);
+
+        // Shrink the window from the left if we have more than k distinct characters
+        while (characterCount.size > k) {
+            const leftChar = s[left];
+            characterCount.set(leftChar, characterCount.get(leftChar)! - 1);
+            // Remove the character from the map if its count drops to zero
+            if (characterCount.get(leftChar) === 0) {
+              characterCount.delete(leftChar);
+            }
+            left++;
+        }
+
+        // Update the maximum length found so far
+        maxLength = Math.max(maxLength, right - left + 1);
+    }
+
+    return maxLength;
+};