leetcode

commit 4349ad85a06f47f84abbfbdb98427083ed5ca430
parent e608af56c0aba66323fb253f4bd2dfe3d2b38fb8
Author: Jack Sangdahl <jack@pngu.org>
Date:   Sun, 13 Jul 2025 21:16:55 -0600

1290. convert binary number in a linked list to integer

Diffstat:
A
convert_bin_ll_int.c
 | 
30
++++++++++++++++++++++++++++++
A
convert_bin_ll_int.py
 | 
36
++++++++++++++++++++++++++++++++++++

2 files changed, 66 insertions(+), 0 deletions(-)
diff --git a/convert_bin_ll_int.c b/convert_bin_ll_int.c
@@ -0,0 +1,30 @@
+// 1290. Convert Binary Number in a Linked List to Integer
+#include "leetcode.h"
+
+/*
+ * given 'head' which is a reference node to a singly linked list. the value of
+ * each node in the linked list is either 0 or 1. the linked list holds the
+ * binary representation of a number. return the decimal value of the number in
+ * the linked list. the most significant bit is at the head of the linked list.
+ */
+
+int getDecimalValue(struct ListNode *head) {
+  int ans = 0;
+  while (head) {
+    ans <<= 1;
+    ans += head->val;
+    head = head->next;
+  }
+  return ans;
+}
+
+int main() {
+  struct ListNode *h1 = listnode_create(1);
+  h1->next = listnode_create(0);
+  h1->next->next = listnode_create(1);
+  struct ListNode *h2 = listnode_create(0);
+  printf("%d\n", getDecimalValue(h1)); // expect: 5
+  printf("%d\n", getDecimalValue(h2)); // expect: 0
+  listnode_free(h1);
+  listnode_free(h2);
+}
diff --git a/convert_bin_ll_int.py b/convert_bin_ll_int.py
@@ -0,0 +1,36 @@
+# 1290. Convert Binary Number in a Linked List to Integer
+
+"""
+given 'head' which is a reference node to a singly linked list. the value of
+each node in the linked list is either 0 or 1. the linked list holds the
+binary representation of a number. return the decimal value of the number in
+the linked list. the most significant bit is at the head of the linked list.
+"""
+
+
+# Definition for singly-linked list.
+class ListNode(object):
+    def __init__(self, val=0, next=None):
+        self.val = val
+        self.next = next
+
+
+class Solution(object):
+    def getDecimalValue(self, head):
+        """
+        :type head: Optional[ListNode]
+        :rtype: int
+        """
+        ans = 0
+        while head:
+            ans = 2 * ans + head.val
+            head = head.next
+        return ans
+
+
+if __name__ == "__main__":
+    obj = Solution()
+    h1 = ListNode(1, ListNode(0, ListNode(1)))
+    h2 = ListNode(0)
+    print(obj.getDecimalValue(h1))
+    print(obj.getDecimalValue(h2))