Day-19 linkedlist Problems

Author: mandliya

linked_list_problems/add_two_numbers_lists.cpp

@@ -0,0 +1,107 @@
+/*
+ * We have two numbers represented by a linked list, 
+ * where each node contains a single digit. The digits are stored in reverse order,
+ * such that the 1's digit is at the head of the list.
+ * Write a function that adds the two numbers and returns the sum as a linked list.
+ *
+ * Example
+ * Given 7->1->6 + 5->9->2. That is, 617 + 295.
+ *
+ * Return 2->1->9. That is 912.
+ *
+ * Given 3->1->5 and 5->9->2, return 8->0->8.
+ */
+
+#include <iostream>
+
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode(int v): val(v), next(nullptr)
+    { }
+};
+
+ListNode * addLists( ListNode * list1, ListNode *list2 )
+{
+    ListNode *list3 = nullptr;
+    ListNode *curr = nullptr;
+    int carry = 0;
+    while ( list1 && list2 ) {
+        int x = list1->val + list2->val + carry;
+        if ( x  > 9 ) {
+            carry = x / 10;
+            x %= 10;
+        } else {
+            carry = 0;
+        }
+        if (list3 == nullptr) {
+            list3 = new ListNode(x);
+            curr = list3;
+        } else {
+            curr->next = new ListNode(x);
+            curr = curr->next;
+        }
+        list1 = list1->next;
+        list2 = list2->next;
+    }
+
+    while(list1) {
+        int x = list1->val + carry;
+        if ( x  > 9 ) {
+            carry = x / 10;
+            x %= 10;
+        } else {
+            carry = 0;
+        }
+        curr->next = new ListNode(x);
+        curr = curr->next;
+        list1 = list1->next;
+    }
+    while(list2) {
+        int x = list2->val + carry;
+        if ( x  > 9 ) {
+            carry = x / 10;
+            x %= 10;
+        } else {
+            carry = 0;
+        }
+        curr->next = new ListNode(x);
+        curr = curr->next;
+        list2 = list2->next;
+    }
+    if (carry > 0) {
+        curr->next = new ListNode(carry);
+        curr  = curr->next;
+    }
+    return list3;
+}
+
+void iterate(ListNode *node) {
+    while (node) {
+        std::cout << node->val << " ";
+        node = node->next;
+    }
+    std::cout << std::endl;
+}
+
+int main()
+{
+    ListNode *list1, *list2;
+    list1 = new ListNode(9);
+    list1->next = new  ListNode(9);
+
+    list2 = new ListNode(5);
+    list2->next = new ListNode(9);
+    list2->next->next = new ListNode(2);
+
+    iterate(list1);
+    iterate(list2);
+    ListNode *list3 = addLists(list1, list2);
+    iterate(list3);
+
+    
+
+
+    return 0;
+
+}

linked_list_problems/nthToLastNode.cpp

@@ -0,0 +1,69 @@
+/*
+ * Find nth to last node in a linked list.
+ *
+ */
+
+
+
+#include<iostream>
+
+
+struct ListNode {
+    int val;
+    ListNode *next;
+    ListNode(int v): val{v}, next{nullptr} { }
+};
+
+ListNode* nthToLastNode( ListNode *head, int n )
+{
+    ListNode *ptr1 = head;
+    ListNode *ptr2 = head;
+
+    int i = 1;
+    while ( ptr1 && i <= n) {
+        ptr1 = ptr1->next;
+        ++i;
+    }
+    while( ptr1) {
+        ptr1 = ptr1->next;
+        ptr2 = ptr2->next;
+    }
+    return ptr2;
+}
+
+void insert( ListNode* & head, int v )
+{
+    ListNode *newNode = new ListNode(v);
+    if ( head == nullptr) {
+        head = newNode;
+    } else {
+        ListNode *temp = head;
+        while( temp->next != nullptr ) {
+            temp = temp->next;
+        }
+        temp->next = newNode;
+    }
+}
+
+void iterateList(ListNode *head) {
+    while(head) {
+        std::cout << head->val << "-->";
+        head = head->next;
+    }
+    std::cout << "NULL" <<  std::endl;
+}
+
+int main()
+{
+    ListNode * head = nullptr;
+    insert(head, 3);
+    insert(head, 2);
+    insert(head, 1);
+    insert(head, 5);
+    iterateList(head);
+
+    ListNode *nthNodeToLastNode = nthToLastNode(head, 2);
+    std::cout << nthNodeToLastNode->val << std::endl;
+
+}
+