[shinsj4653] Week 08 Solutions

clone-graph/shinsj4653.py

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+"""
+[문제풀이]
+# Inputs
+
+# Outputs
+
+# Constraints
+
+# Ideas
+
+[회고]
+
+"""
+
+
+# Definition for a Node.
+class Node:
+    def __init__(self, val=0, neighbors=None):
+        self.val = val
+        self.neighbors = neighbors if neighbors is not None else []
+
+
+from typing import Optional
+from collections import deque
+
+
+class Solution:
+    def cloneGraph(self, node: Optional['Node']) -> Optional['Node']:
+
+        if not node:
+            return
+
+        clone = Node(node.val)
+        clones = {node: clone}
+
+        q = deque([node])  # 해당 라인 답지 참고
+
+        while q:
+            node = q.popleft()
+
+            for nei in node.neighbors:
+                if nei not in clones:
+                    clones[nei] = Node(nei.val)  # 답지 참고
+                    q.append(nei)
+
+                clones[node].neighbors.append(clones[nei])  # 답지 참고
+
+        return clone
+
+

longest-common-subsequence/shinsj4653.py

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+"""
+[문제풀이]
+# Inputs
+
+# Outputs
+
+# Constraints
+
+# Ideas
+
+[회고]
+
+"""
+
+
+class Solution:
+    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
+        n, m = len(text1), len(text2)
+        dp = [[0 for _ in range(m + 1)] for _ in range(n + 1)]
+
+        for i in range(1, n + 1):
+            for j in range(1, m + 1):
+                if text1[i - 1] == text2[j - 1]:
+                    dp[i][j] = dp[i - 1][j - 1] + 1
+
+                else:
+                    dp[i][j] = max(dp[i - 1][j], dp[i][j - 1])
+
+        return dp[n][m]
+

longest-repeating-character-replacement/shinsj4653.py

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+"""
+[문제풀이]
+# Inputs
+
+# Outputs
+
+# Constraints
+
+# Ideas
+
+[회고]
+
+"""
+class Solution:
+    def characterReplacement(self, s: str, k: int) -> int:
+        max_len = 0
+        counter = {}
+        start, end = 0, 0
+        while end < len(s):
+            counter[s[end]] = counter.get(s[end], 0) + 1
+            while end - start + 1 - max(counter.values()) > k:
+                counter[s[start]] -= 1
+                start += 1
+            max_len = max(end - start + 1, max_len)
+            end += 1
+        return max_len
+

palindromic-substrings/shinsj4653.py

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+"""
+[문제풀이]
+# Inputs
+string  s
+
+# Outputs
+the number of palindromic substrings
+
+# Constraints
+1 <= s.length <= 1000
+s consists of lowercase English letters.
+
+# Ideas
+부분 문자열 중 팰린드롬 인거
+순열?
+10^3 => 시초 예상
+
+코드를 짜보니 O(n^3) 나오긴하는데 우선 정답
+
+[회고]
+
+"""
+
+
+class Solution:
+    def countSubstrings(self, s: str) -> int:
+        ret = 0
+
+        for num in range(1, len(s) + 1):
+            for i in range(len(s) - num + 1):
+                ss = s[i:i + num]
+                if ss == ss[::-1]:
+                    ret += 1
+
+        return ret
+
+# 해설보고 스스로 풀이
+
+class Solution:
+    def countSubstrings(self, s: str) -> int:
+        dp = {}
+
+        for start in range(len(s)):
+            for end in range(start, -1, -1):
+                if start == end:
+                    dp[(start, end)] = True
+
+                elif start + 1 == end:
+                    dp[(start, end)] = s[start] == s[end]
+
+                else:
+                    dp[(start, end)] = dp[(start + 1, end - 1)] and s[start] == s[end]
+
+        return dp.values().count(True)
+
+# 기존 값 재활용하려면 end 부터 세야하는게 이해가 안감
+# -> 다시 풀이
+class Solution:
+    def countSubstrings(self, s: str) -> int:
+        dp = {}
+
+        for end in range(len(s)):
+            for start in range(end, -1, -1):
+                if start == end:
+                    dp[(start, end)] = True
+
+                elif start + 1 == end:
+                    dp[(start, end)] = s[start] == s[end]
+
+                else:
+                    dp[(start, end)] = dp[(start + 1, end - 1)] and s[start] == s[end]
+
+        return list(dp.values()).count(True)
+

reverse-bits/shinsj4653.py

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+"""
+[문제풀이]
+# Inputs
+
+# Outputs
+
+# Constraints
+
+# Ideas
+
+[회고]
+
+"""
+
+
+class Solution:
+    def reverseBits(self, n: int) -> int:
+        st = []
+
+        # while n > 0:
+        #    st.append(n % 2)
+        #    n //= 2  => 32 bit 길이 맞춰야함!
+
+        while len(st) < 32:
+            print('st.append: ', n % 2)
+            st.append(n % 2)
+            n //= 2
+
+        ret, num = 0, 0
+        print("st: ", st)
+
+        # 6 : 110
+        # [0 1 1]
+
+        while st:
+            print('st.pop(): ', st[-1])
+            ret += st.pop() * (2 ** num)
+            num += 1
+
+        return ret
+
+