2023-07-17 Daily Challenge

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In: DailyChallenge

Today I have done leetcode's July LeetCoding Challenge with cpp.

July LeetCoding Challenge 17

Description

Add Two Numbers II

You are given two non-empty linked lists representing two non-negative integers. The most significant digit comes first 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.

 

Example 1:

Input: l1 = [7,2,4,3], l2 = [5,6,4]
Output: [7,8,0,7]

Example 2:

Input: l1 = [2,4,3], l2 = [5,6,4]
Output: [8,0,7]

Example 3:

Input: l1 = [0], l2 = [0]
Output: [0]

 

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.

 

Follow up: Could you solve it without reversing the input lists?

Solution

auto speedup = [](){
  cin.tie(nullptr);
  cout.tie(nullptr);
  ios::sync_with_stdio(false);
  return 0;
}();
class Solution {
  pair<ListNode*, int> addTwoNumber(ListNode* l1, int len1, ListNode* l2, int len2) {
    if(!len1 || !len2) return len1 ? make_pair(l1, 0) : make_pair(l2, 0);
    ListNode *nextNode;
    int carry, curVal;
    if(len1 > len2) {
      tie(nextNode, carry) = addTwoNumber(l1->next, len1-1, l2, len2);
      curVal = l1->val + carry;
    } else if(len1 < len2) {
      tie(nextNode, carry) = addTwoNumber(l1, len1, l2->next, len2-1);
      curVal = l2->val + carry;
    } else {
      tie(nextNode, carry) = addTwoNumber(l1->next, len1-1, l2->next, len2-1);
      curVal = l1->val +l2->val + carry;
    }
    ListNode *node = new ListNode(curVal%10, nextNode);
    return make_pair(node, curVal/10);
  }
  
  int length(ListNode* l) {
    int len = 0;
    while(l) {
      len += 1;
      l = l->next;
    }
    return len;
  }
public:
  ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
    int len1 = length(l1);
    int len2 = length(l2);
    auto [head, carry] = addTwoNumber(l1, len1, l2, len2);
    if(!carry) return head;
    return new ListNode(carry, head);
  }
};

// Accepted
// 1563/1563 cases passed (36 ms)
// Your runtime beats 73.8 % of cpp submissions
// Your memory usage beats 32.62 % of cpp submissions (71.6 MB)
Algorithm