[chapse57] Week 3

climbing-stairs/chapse57.py

@@ -0,0 +1,21 @@
+class Solution(object):
+    def climbStairs(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+
+
+        if n == 1:
+            return 1
+        if n == 2:
+            return 2
+        a = 1
+        b = 2                
+
+        for i in range(n - 2):   
+            c = a + b
+            a = b
+            b = c
+        return c
+

contains-duplicate/chapse57.py

@@ -0,0 +1,11 @@
+class Solution(object):
+    def containsDuplicate(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: bool
+        """
+        for i in range(len(nums)):
+            for j in range(i+1,len(nums)):
+                if nums[i] == nums[j]:
+                    return True
+        return False

group-anagrams/chapse57.py

@@ -0,0 +1,17 @@
+class Solution(object):
+    def groupAnagrams(self, strs):
+        """
+        :type strs: List[str]
+        :rtype: List[List[str]]
+        """
+        seen = {}
+        for word in strs:
+            key = "".join(sorted(word))
+    # key가 seen에 이미 있으면 → word 추가
+    # 없으면 → 새로 만들기
+            if key in seen:
+                seen[key].append(word)
+            else:
+                seen[key] = [word] 
+        return list(seen.values())
+

top-k-frequent-elements/chapse57.py

@@ -0,0 +1,22 @@
+class Solution(object):
+    def topKFrequent(self, nums, k):
+        """
+        :type nums: List[int]
+        :type k: int
+        :rtype: List[int]
+        """
+        count = {}
+        for n in nums:
+            if n in count:
+                count[n] +=1
+            else:
+                count[n] =1      
+                # count.items()를 횟수 큰 순으로 정렬
+        freq = sorted(count.items(), key=lambda x: x[1], reverse=True)
+
+        result = []
+        for x in freq[:k]:
+            result.append(x[0])
+        return result
+
+

two-sum/chapse57.py

@@ -0,0 +1,14 @@
+class Solution(object):
+    def twoSum(self, nums, target):
+        """
+        :type nums: List[int]
+        :type target: int
+        :rtype: List[int]
+        """
+        seen = {}
+        for i in range(len(nums)):
+            if (target - nums[i]) in seen:
+                return [seen[target - nums[i]],i]   
+            seen[nums[i]] =i
+
+

valid-anagram/chapse57.py

@@ -0,0 +1,11 @@
+class Solution(object):
+    def isAnagram(self, s, t):
+        """
+        :type s: str
+        :type t: str
+        :rtype: bool
+        """
+        return sorted(s) == sorted(t)
+
+
+