Category: DS & Algo

Add Two Numbers – Leetcode Solution

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 contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4 )
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807

# Definition for singly-linked list.
# class ListNode:
#     def __init__(self, x):
#         self.val = x
#         self.next = None

class Solution:
    def addTwoNumbers(self, l1, l2):
        """
        :type l1: ListNode
        :type l2: ListNode
        :rtype: ListNode
        """
        newList = ListNode(self)
        temp = newList
        
        carry =0
        sumTotal = 0
        
        while l1 or l2 or carry:
            if l1:
                sumTotal =  sumTotal+ l1.val
                l1 = l1.next
            if l2:
                sumTotal = sumTotal + l2.val
                l2 = l2.next
            sumTotal = sumTotal + carry
            carry  = sumTotal//10
            temp.next = ListNode(sumTotal%10)
            sumTotal = 0
            temp  = temp.next
        
        return newList.next

Meeting Rooms – Leetcode Solution

Given an array of meeting time intervals consisting of start and end times [[s1,e1],[s2,e2],...] (si < ei), determine if a person could attend all meetings.

Example 1:

Input: [[0,30],[5,10],[15,20]]
Output: false

Example 2:

put: [[7,10],[2,4]]
Output: True
class Solution:
    def canAttendMeetings(self, intervals: List[List[int]]) -> bool:
        start = 0
        end = 1
        intervals.sort()
        print(intervals)
        for i in range(1, len(intervals)):
            if intervals[i][start] < intervals[i-1][end]:
                return False

        return True

Two Sum – Leetcode Solution

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:

Given mums = [2,7,11,15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0,1]

def twoSum(self, nums, target):
        """
        :type nums: List[int]
        :type target: int
        :rtype: List[int]
        """
        
        for i in range(len(nums)):
            for j in range(i+1, len(nums)):
                add = nums[i] + nums[j]
                if(add == target):
                    sums = [i,j]
        return sums