restarting ...

Author: zq29

Franklin/addTwoNumbers.java

@@ -0,0 +1,69 @@
+/*
+lc problem 2
+You are given two non-empty linked lists representing two non-negative integers.
+The digits are stored in reverse order and each of their nodes contain a single digit.
+Add the two numbers and return it as a linked list.
+
+You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+
+Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
+Output: 7 -> 0 -> 8
+*/
+
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     int val;
+ *     ListNode next;
+ *     ListNode(int x) { val = x; }
+ * }
+ */
+public class Solution {
+    // My solution
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+        int carry=0;
+        int p = l1.val;
+        int q = l2.val;
+        int sum = p+q+carry;
+        carry = sum/10; sum = sum%10;
+        ListNode ln = new ListNode(sum);
+        ListNode result = ln;
+        l1 = l1.next; l2 = l2.next;
+        while (l1!=null || l2!=null) {
+            p = l1!=null?l1.val:0; l1 = l1!=null?l1.next:null;
+            q = l2!=null?l2.val:0; l2 = l2!=null?l2.next:null;
+            sum = p+q+carry;
+            carry = sum/10; sum = sum%10;
+            ln.next = new ListNode(sum); ln = ln.next;
+        }
+        if (carry>0) {
+            ln.next = new ListNode(1); ln = ln.next;
+        }
+        return result;
+    }
+
+    // Editorial solution
+    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
+        ListNode dummyHead = new ListNode(0);
+        ListNode p = l1, q = l2, curr = dummyHead;
+        int carry = 0;
+        while (p != null || q != null) {
+            int x = (p != null) ? p.val : 0;
+            int y = (q != null) ? q.val : 0;
+            int sum = carry + x + y;
+            carry = sum / 10;
+            curr.next = new ListNode(sum % 10);
+            curr = curr.next;
+            if (p != null) p = p.next;
+            if (q != null) q = q.next;
+        }
+        if (carry > 0) {
+            curr.next = new ListNode(carry);
+        }
+        return dummyHead.next;
+    }
+
+    // instead of doing an extra operation before the start of while loop,
+    // the editorial soln just used a dummyHead var and return dummyHead.next at the end.
+    // Pretty elegant!
+}

Franklin/isPalindrome.java

@@ -0,0 +1,15 @@
+/*
+lc problem 9
+Determine whether an integer is a palindrome.
+*/
+public class Solution {
+	public boolean isPalindrome(int x) {
+		if (x<0) return false;
+		int rev = 0, y = x;
+		while (y!=0) {
+			rev = rev*10 + y%10;
+			y /= 10;
+		}
+		return (x==rev);
+	}
+}

Franklin/isPalindrome.py

@@ -7,11 +7,11 @@ def isPalindrome(self, x):
         :type x: int
         :rtype: bool
         """
-        if (x<0 or ()):
+        if (x<0):
             return False
-        rev = 0
-        while (x!=0):
-            rev = rev*10 + x%10
-            x = x/10
-        return (x==rev or x==rev/10)
-# what's wrong with the if condition?
+
+        rev = 0; y = x
+        while (y!=0):
+            rev = rev*10 + y%10
+            y = y/10
+        return (x==rev)