added problems

AlveeM · AlveeM · commit ccbbf7aca82d · 2021-04-03T11:19:47.000-04:00
diff --git a/leetcode/top-interview-questions/02_medium_collection/09_others/01_sum_of_two_integers.py b/leetcode/top-interview-questions/02_medium_collection/09_others/01_sum_of_two_integers.py
@@ -0,0 +1,15 @@
+class Solution:
+    def getSum(self, a: int, b: int) -> int:
+        mask = 0xFFFFFFFF # 32 bits
+        while(b != 0):
+            s = (a ^ b) & mask
+            c = ((a & b) << 1) & mask
+            a = s & mask
+            b = c & mask
+        
+        max_int = 0x7FFFFFFF
+        
+        if a < max_int:
+            return a 
+        else:
+            return ~(a ^ mask)
diff --git a/leetcode/top-interview-questions/02_medium_collection/09_others/02_evaluate_reverse_polish_notation.py b/leetcode/top-interview-questions/02_medium_collection/09_others/02_evaluate_reverse_polish_notation.py
@@ -0,0 +1,21 @@
+ops = {
+    '+': lambda a, b: a + b,
+    '-': lambda a, b: a - b,
+    '*': lambda a, b: a * b,
+    '/': lambda a, b: int(a / b)
+}
+
+class Solution:
+    def evalRPN(self, tokens: List[str]) -> int:
+        stack = []
+        
+        for token in tokens:
+            if token in ops:
+                num1 = stack.pop()
+                num2 = stack.pop()
+                res = ops[token](num2, num1)
+                stack.append(res)
+            else:
+                stack.append(int(token))
+                
+        return stack[0]
diff --git a/leetcode/top-interview-questions/02_medium_collection/09_others/03_majority_element.py b/leetcode/top-interview-questions/02_medium_collection/09_others/03_majority_element.py
@@ -0,0 +1,14 @@
+class Solution:
+    def majorityElement(self, nums: List[int]) -> int:
+        count = 0
+        candidate = nums[0]
+        
+        for num in nums:
+            if count == 0:
+                candidate = num
+            if num == candidate:
+                count += 1
+            else:
+                count -= 1
+        
+        return candidate
