solve: longest substring without repeating characters

Author: sounmind

longest-substring-without-repeating-characters/evan.js

@@ -0,0 +1,36 @@
+/**
+ * @param {string} str
+ * @return {number}
+ */
+var lengthOfLongestSubstring = function (str) {
+  let maxLength = 0;
+  let left = 0;
+  const lastSeenCharIndexMap = {};
+
+  for (let right = 0; right < str.length; right++) {
+    const currentChar = str[right];
+
+    // If the current character was seen before, update the left pointer
+    if (lastSeenCharIndexMap[currentChar] >= left) {
+      left = lastSeenCharIndexMap[currentChar] + 1;
+    }
+
+    lastSeenCharIndexMap[currentChar] = right;
+
+    maxLength = Math.max(maxLength, right - left + 1);
+  }
+
+  return maxLength;
+};
+
+/**
+ * Time Complexity: O(n)
+ * - The right pointer iterates through the string once, making it O(n).
+ * - The left pointer only moves when a duplicate character is found, ensuring each character is processed at most twice.
+ * - Thus, the total time complexity is O(n).
+ *
+ * Space Complexity: O(min(n, m))
+ * - The space complexity is determined by the size of the character map, which stores the indices of characters in the current window.
+ * - In the worst case, the map could store all unique characters in the string.
+ * - Thus, the space complexity is O(min(n, m)), where n is the length of the string and m is the character set size.
+ */