20231214 Finished

src/solution/mod.rs

@@ -2,3 +2,4 @@ mod s0001_two_sum;
 mod s0009_palindrome_number;
 mod s0020_valid_parentheses;
 mod s2697_lexicographically_smallest_palindrome;
+mod s0002_add_two_numbers;

src/solution/s0002_add_two_numbers.rs

@@ -0,0 +1,122 @@
+/**
+ * [2] Add Two Numbers
+ *
+ * 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 contains a single digit. Add the two numbers and return the sum as a linked list.
+ * You may assume the two numbers do not contain any leading zero, except the number 0 itself.
+ *  
+ * <strong class="example">Example 1:
+ * <img alt="" src="https://assets.leetcode.com/uploads/2020/10/02/addtwonumber1.jpg" style="width: 483px; height: 342px;" />
+ * Input: l1 = [2,4,3], l2 = [5,6,4]
+ * Output: [7,0,8]
+ * Explanation: 342 + 465 = 807.
+ * 
+ * <strong class="example">Example 2:
+ * 
+ * Input: l1 = [0], l2 = [0]
+ * Output: [0]
+ * 
+ * <strong class="example">Example 3:
+ * 
+ * Input: l1 = [9,9,9,9,9,9,9], l2 = [9,9,9,9]
+ * Output: [8,9,9,9,0,0,0,1]
+ * 
+ *  
+ * Constraints:
+ * 
+ * 	The number of nodes in each linked list is in the range [1, 100].
+ * 	0 <= Node.val <= 9
+ * 	It is guaranteed that the list represents a number that does not have leading zeros.
+ * 
+ */
+pub struct Solution {}
+use crate::util::linked_list::{ListNode, to_list};
+
+// problem: https://leetcode.cn/problems/add-two-numbers/
+// discuss: https://leetcode.cn/problems/add-two-numbers/discuss/?currentPage=1&orderBy=most_votes&query=
+
+// submission codes start here
+
+// Definition for singly-linked list.
+// #[derive(PartialEq, Eq, Clone, Debug)]
+// pub struct ListNode {
+//   pub val: i32,
+//   pub next: Option<Box<ListNode>>
+// }
+//
+// impl ListNode {
+//   #[inline]
+//   fn new(val: i32) -> Self {
+//     ListNode {
+//       next: None,
+//       val
+//     }
+//   }
+// }
+impl Solution {
+    pub fn add_two_numbers(l1: Option<Box<ListNode>>, l2: Option<Box<ListNode>>)
+        -> Option<Box<ListNode>> {
+        let (mut left, mut right) = (l1, l2);
+        let mut dummy_head = Some(Box::new(ListNode::new(0)));
+        let mut now = &mut dummy_head;
+        let mut overflow = 0;
+
+        loop {
+            if left.is_none() && right.is_none() && overflow == 0 {
+                break
+            }
+
+            let left_value = match left {
+                None => {
+                    0
+                }
+                Some(node) => {
+                    left = node.next;
+                    node.val
+                }
+            };
+
+            let right_value = match right {
+                None => {
+                    0
+                }
+                Some(node) => {
+                    right = node.next;
+                    node.val
+                }
+            };
+
+            let value = overflow + left_value + right_value;
+            overflow = value / 10;
+
+            now.as_mut().unwrap().next = Some(Box::new(ListNode::new(value % 10)));
+            now = &mut now.as_mut().unwrap().next;
+        }
+
+        dummy_head.unwrap().next
+    }
+}
+
+// submission codes end
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_2() {
+        assert_eq!(
+            Solution::add_two_numbers(to_list(vec![2, 4, 3]), to_list(vec![5, 6, 4])),
+            to_list(vec![7, 0, 8])
+        );
+
+        assert_eq!(
+            Solution::add_two_numbers(to_list(vec![9, 9, 9, 9]), to_list(vec![9, 9, 9, 9, 9, 9])),
+            to_list(vec![8, 9, 9, 9, 0, 0, 1])
+        );
+
+        assert_eq!(
+            Solution::add_two_numbers(to_list(vec![0]), to_list(vec![0])),
+            to_list(vec![0])
+        );
+    }
+}