Array

Coding Test/1.py

@@ -0,0 +1,10 @@
+class Solution:
+    def twoSum(self, nums: List[int], target: int) -> List[int]:
+        num_map = {}
+        for i, num in enumerate(nums):
+            if target - num in num_map and i != num_map[target-num]:
+                return i, num_map[target-num]
+            num_map[num] = i;
+
+
+

Coding Test/121.py

@@ -0,0 +1,10 @@
+class Solution:
+    def maxProfit(self, prices: List[int]) -> int:
+        profit = 0
+        min_price = sys.maxsize
+
+        for price in prices:
+            min_price = min(min_price, price)
+            profit = max(price-min_price, profit)
+
+        return profit

Coding Test/15.py

@@ -0,0 +1,28 @@
+class Solution:
+    def threeSum(self, nums: List[int]) -> List[List[int]]:
+        result = []
+        nums.sort()
+
+
+        for i in range(len(nums) - 2):
+            if i > 0 and nums[i] == nums[i-1]:
+                continue
+
+            left, right = i + 1, len(nums) - 1
+            while left < right:
+                three_sum = nums[i] + nums[left] + nums[right]
+
+                if three_sum < 0:
+                    left += 1
+                elif three_sum > 0:
+                    right -= 1
+                else:
+                    result.append([nums[i], nums[left], nums[right]])
+
+                    while left < right and nums[left] == nums[left + 1]:
+                        left += 1
+                    while left < right and nums[right] == nums[right - 1]:
+                        right -= 1
+                    left += 1
+                    right -= 1
+        return result

Coding Test/238.py

@@ -0,0 +1,32 @@
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        a = [1]
+        b = [1]
+        res = []
+        for i in range(len(nums) - 1):
+            a.append(a[i] * nums[i])
+            b.append(b[i] * nums[-i-1])
+
+        b.reverse()
+
+        for i in range(len(nums)):
+            res.append(a[i] * b[i])
+
+        return res
+
+
+class Solution2:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        out = []
+        p = 1
+
+        for i in range(0, len(nums)):
+            out.append(p)
+            p = p * nums[i]
+        p = 1
+
+        for i in range(len(nums)-1, 0 - 1, -1):
+            out[i] = out[i] * p
+            p = p * nums[i]
+
+        return out

Coding Test/42.py

@@ -0,0 +1,45 @@
+# Stack
+class Solution:
+    def trap(self, height: List[int]) -> int:
+        stck = []
+        result = 0
+
+        for i in range(len(height)):
+            while stck and height[i] > height[stck[-1]]:
+
+                top = stck.pop()
+
+                if not len(stck):
+                    break
+
+                dist = i - stck[-1] - 1
+                water = min(height[i], height[stck[-1]]) - height[top]
+
+                result += dist * water
+
+            stck.append(i)
+
+        return result
+
+# Two pointers
+class Solution2:
+    def trap(self, height: List[int]) -> int:
+        if not height:
+            return 0
+
+        volume = 0
+        left, right = 0, len(height) - 1
+        left_max, right_max = height[left], height[right]
+
+
+        while left < right:
+            left_max, right_max = max(height[left], left_max), max(height[right], right_max)
+
+            if left_max <= right_max:
+                volume += left_max - height[left]
+                left += 1
+            else:
+                volume += right_max - height[right]
+                right -= 1
+        return volume
+

Coding Test/561.py

@@ -0,0 +1,15 @@
+# normal
+class Solution:
+    def arrayPairSum(self, nums: List[int]) -> int:
+        result = 0
+        nums.sort()
+
+        for i in range(0, len(nums)-1, 2):
+            result += nums[i]
+
+        return result
+
+# Pythonic    
+class Solution2:
+    def arrayPairSum(self, nums: List[int]) -> int:
+        return sum(sorted(nums)[::2])

Coding Test/819.py

@@ -1,3 +1,6 @@
+import re
+import collections
+
 class Solution:
     def mostCommonWord(self, paragraph: str, banned: List[str]) -> str:
         words = [word for word in re.sub('[^\w]', ' ', paragraph).lower().split() if word not in banned]

README.md

@@ -1,11 +1,13 @@
 # 자료구조 및 알고리즘 복습
 
-<b>취업을 준비함에 있어 자료구조와 알고리즘 공부는 필수 입니다.</b>
+**취업을 준비함에 있어 자료구조와 알고리즘 공부는 필수 입니다.**
 
 필자는 아래의 주제에 맞춰 C++ 또는 Python 으로 각각을 구현하고자 합니다.
 
 모든 문제는 Leetcode 에 있습니다.
 
+숫자는 Leetcode 문제 번호 입니다.
+
 ## 준비운동
 
 파이썬 문자열 조작
@@ -15,7 +17,7 @@
 ## 자료구조
 
 1. Array
-   >
+   > 1, 42, 15, 561, 238, 121
 2. Stack
 3. Queue
 4. Deque