handled all automated failing tests

data_structure/doubly_linked_list.cpp

@@ -0,0 +1,124 @@
+#include <iostream>
+
+struct node {
+  int val;
+  node *prev;
+  node *next;
+};
+
+node *start;
+
+void insert(int x) {
+  node *t = start;
+  if (start != NULL) {
+    while (t->next != NULL) {
+      t = t->next;
+    }
+    node *n = new node;
+    t->next = n;
+    n->prev = t;
+    n->val = x;
+    n->next = NULL;
+  } else {
+    node *n = new node;
+    n->val = x;
+    n->prev = NULL;
+    n->next = NULL;
+    start = n;
+  }
+}
+
+void remove(int x) {
+  node *t = start;
+  while (t != NULL && t->val != x) {
+    t = t-> next;
+  }
+  if (t == NULL) {
+    return;
+  }
+  if (t->prev == NULL) {
+    if (t->next == NULL) {
+      start = NULL;
+    } else {
+      start = t->next;
+      start->prev = NULL;
+    }
+  } else if (t->next == NULL) {
+    t->prev->next = NULL;
+  } else {
+    t->prev->next = t->next;
+    t->next->prev = t->prev;
+  }
+}
+
+void search(int x) {
+  node *t = start;
+  int found = 0;
+  while (t != NULL) {
+    if (t->val == x) {
+      std::cout << "\nFound";
+      found = 1;
+      break;
+    }
+    t = t->next;
+  }
+  if (found == 0) {
+    std::cout << "\nNot Found";
+  }
+}
+
+void show() {
+  node *t = start;
+  while (t != NULL) {
+    std::cout << t->val << "\t";
+    t = t->next;
+  }
+}
+
+void reverseShow() {
+  node *t = start;
+  while (t->next != NULL) {
+    t = t->next;
+  }
+  while (t != NULL) {
+    std::cout << t->val << "\t";
+    t = t->prev;
+  }
+}
+
+int main() {
+  int choice, x;
+  do {
+    std::cout << "\n1. Insert";
+    std::cout << "\n2. Delete";
+    std::cout << "\n3. Search";
+    std::cout << "\n4. Forward print";
+    std::cout << "\n5. Reverse print";
+    std::cout << "\n\nEnter you choice : ";
+    std::cin >> choice;
+    switch (choice) {
+      case 1:
+        std::cout << "\nEnter the element to be inserted : ";
+        std::cin >> x;
+        insert(x);
+        break;
+      case 2:
+        std::cout << "\nEnter the element to be removed : ";
+        std::cin >> x;
+        remove(x);
+        break;
+      case 3:
+        std::cout << "\nEnter the element to be searched : ";
+        std::cin >> x;
+        search(x);
+        break;
+      case 4:
+        show();
+        break;
+      case 5:
+        reverseShow();
+        break;
+    }
+  } while (choice != 0);
+  return 0;
+}