The Tech Street

Program to Implement - Best Time to Buy and Sell Stock  Say you have an array for which the ith element is the price of a given stock on day i.  If you were only permitted to complete at most one transaction (ie, buy one and sell one share of the stock), design an algorithm to find the maximum profit.  Example 1:  Input: [7, 1, 5, 3, 6, 4]  Output: 5  max. difference = 6-1 = 5 (not 7-1 = 6, as selling price needs to be larger than buying price)  Example 2:  In this case, no transaction is done, i.e. max profit = 0.  Input: [7, 6, 4, 3, 1]  Output: 0  '''  class Solution(object):      def maxProfit(self, prices):          """          :type prices: List[int]          :rtype: int          """                 # Brute Force - O(n^2)          profit = 0          for i in range(0,len(prices)):              for j in range(i+1,len(prices)):                  if(prices[j] > prices[i] and profit < prices[j] - prices[i]): 

Pairwise swap elements of a given linked list by changing links -  class Solution(object):          #Iterative Solution          def swapPairs(self, head):          """          :type head: ListNode          :rtype: ListNode          """          if(head is None or head.next is None):              return head                        curr = head.next          prev = head          head = curr                    while(True):              sec = curr.next              curr.next = prev                            if(sec is None or sec.next is None):                  prev.next = sec                  break                            prev.next = sec.next              prev = sec              curr.next = prev          return head              #Recursively Solution     def swapPairs(self, head):          """          :type head: ListNode          :rtype: ListNode          """          if not head or not

#Sum of Two Integers Calculate the sum of two integers a and b, but you are not allowed to use the operator + and -. class Solution(object):     def getSum(self, a, b):         """         :type a: int         :type b: int         :rtype: int         """         #Works For Positive and Negative          if (a == 0): return b         if (b == 0): return a         if (a == 2147483647 and b == -2147483648): return -1         flag = False         if (a < 0 and b < 0):             a = -a             b = -b             flag = True         mask = 0xffffffff         while (b != 0):             a = a & mask             b = b & mask             carry = a & b & mask             a = a ^ b             b = (carry << 1) & mask        return -a if flag else a def getSum(self, a, b): # Works Only For Positive numbers carry = 0 if (a == 0): return b if (b == 0): return a