Solution of 159 and 170 problems

Author: Garvit244

100-200q/159.py

@@ -0,0 +1,32 @@
+'''
+Given a string, find the longest substring that contains only two unique characters. For example, given "abcbbbbcccbdddadacb", the longest substring that contains 2 unique character is "bcbbbbcccb".
+'''
+
+class Solution(object):
+	def lengthOfLongestSubstringTwoDistinct(self, s):
+		"""
+        :type s: str
+        :rtype: int 
+        """
+        if not s:
+        	return 0
+
+        unique_char, start, result = {}, 0, 0
+        for index, char in enumerate(s):
+        	if char in unique_char:
+        		unique_char[s] += 1
+        	else:
+        		unique_char[s] = 1
+
+        	if len(unique_char) <= 2:
+        		result = max(result, index-start+1)
+        	else:
+        		while len(unique_char) > 2:
+        			char_index = s[start]
+        			count = unique_char[char_index]
+        			if count == 1:
+        				del unique_char[char_index]
+        			else:
+        				unique_char[char_index] -= 1
+        			start += 1
+        return result

100-200q/170.py

@@ -0,0 +1,46 @@
+'''
+Design and implement a TwoSum class. It should support the following operations: add and find.
+
+add – Add the number to an internal data structure.
+find – Find if there exists any pair of numbers which sum is equal to the value.
+
+For example,
+add(1); add(3); add(5);
+find(4) -> true
+find(7) -> false
+'''
+
+class TwoSum(object):
+
+    def __init__(self):
+        """
+        initialize your data structure here
+        """
+        self.value_count = {}
+
+    def add(self, number):
+        """
+        Add the number to an internal data structure.
+        :rtype: nothing
+        """
+        if number in self.value_count:
+        	self.value_count[number] += 1
+        else:
+        	self.value_count[number] = 1
+
+    def find(self, value):
+        """
+        Find if there exists any pair of numbers which sum is equal to the value.
+        :type value: int
+        :rtype: bool
+        """
+        for val in self.value_count:
+        	diff = value - val
+        	if diff in self.value_count and (diff != val or self.value_count[val] > 1):
+        		return True
+        return False
+
+# Your TwoSum object will be instantiated and called as such:
+# twoSum = TwoSum()
+# twoSum.add(number)
+# twoSum.find(value)

README.md

@@ -118,8 +118,10 @@ Python solution of problems from [LeetCode](https://leetcode.com/).
 |191|[Number of 1 Bits](https://leetcode.com/problems/number-of-1-bits/)| [Python](./100-200q/191.py)|Easy|
 |179|[Largest Number](https://leetcode.com/problems/largest-number/) | [Python](./100-200q/179.py)|Medium|
 |173|[Binary Search Tree Iterator](https://leetcode.com/problems/binary-search-tree-iterator)|[Python](./100-200q/173.py)|Medium|
+|170|[Two Sum III - Data structure design](https://leetcode.com/problems/two-sum-iii-data-structure-design)|[Python](./100-200q/170.py)|Easy|
 |162|[Find Peak Element](https://leetcode.com/problems/find-peak-element/) | [Python](./100-200q/162.py)|Medium|
 |160|[Intersection of Two Linked Lists](https://leetcode.com/problems/intersection-of-two-linked-lists/) | [Python](./100-200q/160.py)|Easy|
+|159|[Longest Substring Which Contains 2 Unique Characters](https://leetcode.com/problems/longest-substring-with-at-most-two-distinct-characters)|[Python](./100-200q/159.py)|Hard|
 |155|[Min Stack](https://leetcode.com/problems/min-stack/)| [Python](./100-200q/155.py)|Easy|
 |152|[Maximum Product Subarray](https://leetcode.com/problems/maximum-product-subarray/)| [Python](./100-200q/152.py)|Medium|
 |150|[Evaluate Reverse Polish Notation](https://leetcode.com/problems/evaluate-reverse-polish-notation/)|[Python](./100-200q/150.py)|Medium|