Adding solution os 61, 65, 66, 67 problems

Author: Garvit244

61.py

@@ -0,0 +1,34 @@
+# Definition for singly-linked list.
+# class ListNode(object):
+#     def __init__(self, x):
+#         self.val = x
+#         self.next = None
+
+class Solution(object):
+    def rotateRight(self, head, k):
+        """
+        :type head: ListNode
+        :type k: int
+        :rtype: ListNode
+        """
+        if k == 0:
+        	return head
+        if not head:
+        	return None
+
+        tempHead, length = head, 1
+        while tempHead.next:
+        	length += 1
+        	tempHead = tempHead.next
+
+        tempHead.next = head
+        jump = (length-k)%length
+
+        previous = tempHead
+        while jump > 0:
+        	previous = previous.next
+        	jump -= 1
+        head = previous.next
+        previous.next = None
+
+        return head

65.py

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+'''
+	Validate if a given string is numeric.
+
+	Some examples:
+	"0" => true
+	" 0.1 " => true
+	"abc" => false
+	"1 a" => false
+	"2e10" => true
+
+	Note: It is intended for the problem statement to be ambiguous. You should gather all requirements up front before implementing one.
+'''
+
+class Solution(object):
+    def isNumber(self, s):
+        """
+        :type s: str
+        :rtype: bool
+        """
+        s = s.strip()
+        try:
+            if isinstance(float(s),float) or isinstance(int(s),int):
+                return True
+        except Exception as e:
+            return False
+
+# Time: O(1)
+# Space: O(1)

66.py

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+'''
+	Given a non-empty array of digits representing a non-negative integer, plus one to the integer.
+
+	The digits are stored such that the most significant digit is at the head of the list, and each element in the array contain a single digit.
+
+	You may assume the integer does not contain any leading zero, except the number 0 itself.
+
+	Example 1:
+
+	Input: [1,2,3]
+	Output: [1,2,4]
+	Explanation: The array represents the integer 123
+'''
+
+class Solution(object):
+    def plusOne(self, digits):
+        """
+        :type digits: List[int]
+        :rtype: List[int]
+        """
+        result = []
+        if not digits:
+        	return []
+
+        carry = 1
+        new_digits = digits[::-1]
+
+        for index in range(len(new_digits)):
+        	new_digits[index], carry = (new_digits[index] + carry)%10, (new_digits[index] + carry)/10
+
+        if carry > 0:
+        	new_digits.append(carry)
+        return new_digits[::-1]
+
+Time: O(N)
+Space: O(1)

67.py

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+'''
+	Given two binary strings, return their sum (also a binary string).
+
+	The input strings are both non-empty and contains only characters 1 or 0.
+
+	Example 1:
+
+	Input: a = "11", b = "1"
+	Output: "100"
+
+	Example 2:
+
+	Input: a = "1010", b = "1011"
+	Output: "10101"
+'''
+
+class Solution(object):
+    def addBinary(self, a, b):
+        """
+        :type a: str
+        :type b: str
+        :rtype: str
+        """
+        
+        result = ""
+
+        carry = 0
+        index_a, index_b = len(a)-1, len(b)-1
+        while index_a >= 0 and index_b >= 0:
+        	result = (int(a[index_a]) + int(b[index_b]) + carry)%2 + result
+        	carry = (int(a[index_a]) + int(b[index_b]) + carry)%2
+        	index_a -= 1
+        	index_b -= 1
+
+        if index_a >= 0:
+        	while index_a >= 0:
+	        	result = (int(a[index_a]) + carry)%2 + result
+	        	carry = (int(a[index_a]) + carry)%2
+	        	index_a -= 1
+	    elif index_b >= 0:
+	    	while index_b >= 0:
+	    		result = (int(b[index_b]) + carry)%2 + result
+	    		carry = (int(b[index_b]) + carry)%2
+	    		index_b -= 1
+	    else:
+	    	if carry == 1:
+	    		result = str(carry) + result
+	    return result