[ayosecu] Week 08 Solutions

clone-graph/ayosecu.py

@@ -0,0 +1,85 @@
+from typing import Optional
+from collections import deque
+
+# 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 []
+
+class Solution:
+    """
+        - Time Complexity: O(N + E)
+            - N = The number of nodes
+            - E = The number of neighbors
+        - Space Complexity: O(N + E)
+    """
+    def cloneGraph(self, node: Optional['Node']) -> Optional['Node']:
+        if not node:
+            return None
+
+        dq = deque([node])
+        dic = {}
+        dic[node] = Node(node.val)
+
+        while dq:
+            pop_node = dq.popleft()        
+
+            for n in pop_node.neighbors:
+                if n not in dic:
+                    dq.append(n)
+                    dic[n] = Node(n.val)
+                dic[pop_node].neighbors.append(dic[n])
+
+        return dic[node]             
+
+
+### TEST CASES ###
+def build_graph(adj_list):
+    if not adj_list:
+        return None
+
+    nodes = {}
+    for i in range(1, len(adj_list) + 1):
+        nodes[i] = Node(i)
+
+    for i, neighbors in enumerate(adj_list, 1):
+        nodes[i].neighbors = [nodes[n] for n in neighbors]
+
+    return nodes[1]
+
+
+def print_graph(node):
+    if not node:
+        print("None")
+        return
+
+    visited = set()
+    q = deque([node])
+    while q:
+        curr = q.popleft()
+        if curr in visited:
+            continue
+        visited.add(curr)
+        print(f"Node {curr.val}: {[n.val for n in curr.neighbors]}")
+        for neighbor in curr.neighbors:
+            if neighbor not in visited:
+                q.append(neighbor)
+
+tc = [
+        [[2,4],[1,3],[2,4],[1,3]],
+        [[]],
+        []
+]
+
+sol = Solution()
+for i, adj_list in enumerate(tc, 1):
+    original = build_graph(adj_list)
+    print(f"===== TC {i} =====")
+    print("Original Graph:")
+    print_graph(original)
+
+    cloned = sol.cloneGraph(original)
+
+    print("\nCloned Graph:")
+    print_graph(cloned)

longest-common-subsequence/ayosecu.py

@@ -0,0 +1,31 @@
+class Solution:
+    """
+        - Time Complexity: O(mn), m = len(text1), n = len(text2)
+        - Space Complexity: O(mn), The size of the dp variable
+    """
+    def longestCommonSubsequence(self, text1: str, text2: str) -> int:
+        m, n = len(text1), len(text2)
+        dp = [ [0] * (n + 1) for _ in range(m + 1) ]
+
+        for i in range(m):
+            for j in range(n):
+                if text1[i] == text2[j]:
+                    # if matched, increase length
+                    dp[i + 1][j + 1] = dp[i][j] + 1
+                else:
+                    # if unmatched, select a larger length from left and up position
+                    dp[i + 1][j + 1] = max(dp[i + 1][j], dp[i][j + 1])
+
+        return dp[m][n]
+
+
+tc = [
+        ("abcde", "ace", 3),
+        ("abc", "abc", 3),
+        ("abc", "def", 0) 
+]
+
+sol = Solution()
+for i, (s1, s2, e) in enumerate(tc, 1):
+    r = sol.longestCommonSubsequence(s1, s2)
+    print(f"TC {i} is Passed!" if r == e else f"TC {i} is Failed! - Expected: {e}, Result: {r}")

longest-repeating-character-replacement/ayosecu.py

@@ -0,0 +1,37 @@
+class Solution:
+    """
+        - Time Complexity: O(n), n = len(s)
+        - Space Complexity: O(1)
+    """
+    def characterReplacement(self, s: str, k: int) -> int:      
+        cnt_arr = [0] * 26
+        max_cnt, max_len = 0, 0
+
+        # Two pointers: left/right
+        l = 0
+        for r in range(len(s)):
+            # Increase count and find max count by right pointer's alphabet
+            idx = ord(s[r]) - ord("A")
+            cnt_arr[idx] += 1
+            max_cnt = max(max_cnt, cnt_arr[idx])
+
+            # Left pointer moves if changable characters exceed k
+            if (r - l + 1) - max_cnt > k:
+                idx = ord(s[l]) - ord("A")
+                cnt_arr[idx] -= 1
+                l += 1
+
+            # Update the max length
+            max_len = max(max_len, r - l + 1)
+
+        return max_len
+
+tc = [
+        ("ABAB", 2, 4),
+        ("AABABBA", 1, 4)
+]
+
+sol = Solution()
+for i, (s, k, e) in enumerate(tc, 1):
+    r = sol.characterReplacement(s, k)
+    print(f"TC {i} is Passed!" if r == e else f"TC {i} is Failed! - Expected: {e}, Result: {r}")

palindromic-substrings/ayosecu.py

@@ -0,0 +1,31 @@
+class Solution:
+    """
+        - Time Complexity: O(n^2), n = len(s)
+        - Space Complexity: O(1)
+    """
+    def countSubstrings(self, s: str) -> int:
+        count = 0
+
+        def checkSide(l, r):
+            cnt = 0
+            while l >= 0 and r < len(s) and s[l] == s[r]:
+                cnt += 1
+                l -= 1
+                r += 1
+            return cnt
+
+        for i in range(len(s)):
+            count += checkSide(i, i)        # Odd case
+            count += checkSide(i, i + 1)    # Even case
+
+        return count
+
+tc = [
+        ("abc", 3),
+        ("aaa", 6)
+]
+
+sol = Solution()
+for i, (s, e) in enumerate(tc, 1):
+    r = sol.countSubstrings(s)
+    print(f"TC {i} is Passed!" if r == e else f"TC {i} is Failed! - Expected: {e}, Result: {r}")

reverse-bits/ayosecu.py

@@ -0,0 +1,24 @@
+class Solution:
+    """
+        - Time Complexity: O(1), 32 times calculation
+        - Space Complexity: O(1)
+    """
+    def reverseBits(self, n: int) -> int:
+        result = 0
+
+        for _ in range(32):
+            result <<= 1
+            result |= n & 1
+            n >>= 1
+
+        return result
+
+tc = [
+        (43261596, 964176192),
+        (4294967293, 3221225471)
+]
+
+sol = Solution()
+for i, (n, e) in enumerate(tc, 1):
+    r = sol.reverseBits(n)
+    print(f"TC {i} is Passed!" if r == e else f"TC {i} is Failed! - Expected: {e}, Result: {r}")