diff --git a/001-100/5. Longest Palindromic Substring.md b/001-100/5. Longest Palindromic Substring.md
index 621c252..ce66690 100644
--- a/001-100/5. Longest Palindromic Substring.md	
+++ b/001-100/5. Longest Palindromic Substring.md	
@@ -65,3 +65,38 @@ var expandAroundCenter = function (s, left, right) {
 
 * Time complexity : O(n^2).
 * Space complexity : O(1).
+
+
+```js
+/**
+ * @param {string} s
+ * @return {string}
+ */
+var longestPalindrome = function(s) {
+    let startIndex = 0;
+    let maxLength = 1;
+    
+    function expandAroundCenter(left, right) {
+        while (left >=0 && right < s.length && s[left] === s[right]) {
+            const currentPalLength = right - left + 1;
+            if (currentPalLength > maxLength) {
+                maxLength = currentPalLength;
+                startIndex = left;
+            }
+            left -= 1;
+            right += 1;
+        }
+    }
+    
+    for (let i = 0; i < s.length; i++) {
+            expandAroundCenter(i-1, i+1);
+            expandAroundCenter(i, i+1);
+        }
+    
+    return s.slice(startIndex, startIndex + maxLength)
+};
+```
+**Complexity:**
+
+* Time complexity : O(n^2).
+* Space complexity : O(1).
diff --git a/101-200/125. Valid Palindrome.md b/101-200/125. Valid Palindrome.md
index 4c67e40..cfed0d7 100644
--- a/101-200/125. Valid Palindrome.md	
+++ b/101-200/125. Valid Palindrome.md	
@@ -61,3 +61,34 @@ nope.
 
 * Time complexity : O(n).
 * Space complexity : O(n).
+
+
+```js
+/**
+ * @param {string} s
+ * @return {boolean}
+ */
+var isPalindrome = function(s) {
+    
+    s = s.toLowerCase().replace(/[\W_]/g, '');
+    
+    let left = 0;
+    let right = s.length - 1;
+    
+    while (left < right) {
+        if (s[left] !== s[right])  {
+            return false
+        }
+        left++;
+        right--;
+    }
+    
+    return true;
+    
+};
+```
+
+**Complexity:**
+
+* Time complexity : O(n).
+* Space complexity : O(1). left and right pointers take the constant space.