[main] Added leetcode problem

Author: cthacker-udel

pythonProblems/leetcode/3sum.py

@@ -0,0 +1,31 @@
+from typing import List
+
+
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        nums = sorted(nums)
+        triplets = []
+        num_len = len(nums)
+        for i, a in enumerate(nums):
+            if i > 0 and a == nums[i - 1]:
+                continue
+            b = i + 1
+            c = num_len - 1
+            while b < c:
+                the_sum = a + nums[b] + nums[c]
+                if the_sum > 0:
+                    c -= 1
+                elif the_sum < 0:
+                    b += 1
+                else:
+                    triplets.append([a, nums[b], nums[c]])
+                    b += 1
+                    while nums[b] == nums[b - 1] and b < c:
+                        b += 1
+        return triplets
+
+
+if __name__ == '__main__':
+    sol = Solution()
+    print(sol.threeSum([-1, 0, 1, 2, -1, -4]
+                       ))

pythonProblems/leetcode/letterCombinations.py

@@ -0,0 +1,53 @@
+from typing import List
+import itertools
+
+combos = {
+    2: ["a", "b", "c"],
+    3: ["d", "e", "f"],
+    4: ["g", "h", "i"],
+    5: ["j", "k", "l"],
+    6: ["m", "n", "o"],
+    7: ["p", "q", "r", "s"],
+    8: ["t", "u", "v"],
+    9: ["w", "x", "y", "z"]
+}
+
+
+def generate_perms(k, arr):
+    if k == 1:
+        print(arr)
+        return arr
+    else:
+        generate_perms(k - 1, arr)
+
+        for i in range(k):
+            generate_perms(k - 1, arr)
+
+            if k % 2 != 0:
+                arr[0], arr[k - 1] = arr[k - 1], arr[0]
+            else:
+                arr[i], arr[k - 1] = arr[k - 1], arr[i]
+
+
+class Solution:
+    def letterCombinations(self, digits: str) -> List[str]:
+        representations = ["0", "1", "abc", "def",
+                           "ghi", "jkl", "mno", "pqrs", "tuv", "wxyz"]
+        queue = []
+        if len(digits) == 0:
+            return queue
+        queue.append("")
+
+        for i in range(len(digits)):
+            ind = int(digits[i])
+            while len(queue[0]) == i:
+                permutation = queue[0]
+                del queue[0]
+                for eachchar in representations[ind]:
+                    queue.append(permutation + eachchar)
+        return queue
+
+
+if __name__ == '__main__':
+    sol = Solution()
+    print(sol.letterCombinations("23"))

pythonProblems/leetcode/threeSumClosest.py

@@ -0,0 +1,30 @@
+from typing import List
+
+
+class Solution:
+    def threeSumClosest(self, nums: List[int], target: int) -> int:
+        nums.sort()
+        closest_num = nums[0] + nums[1] + nums[2]
+        for i in range(num_len - 2):
+            l_ = i + 1
+            r_ = num_len - 1
+            while l_ < r_:
+                res = nums[i] + nums[l_] + nums[r_]
+                if res == target:
+                    return res
+
+                if abs(target - res) < abs(closest_num - target):
+                    closest_num = res
+
+                if res > target:
+                    r_ -= 1
+                else:
+                    l_ += 1
+        return closest_num
+
+
+if __name__ == '__main__':
+    sol = Solution()
+    print(sol.threeSumClosest([0, 1, 2],
+                              3
+                              ))