[sangbeenmoon] WEEK 04 Solutions (#2756)

* solved same-tree.

* solved top-k-frequent-elements.

* remove outdated files.

* LCS, house-robber.

* week2.

* week3.

* week4.

---------

Co-authored-by: sangbeenmoon <moon.sb@navercorp.com>

Author: sangbeenmoon

coin-change/sangbeenmoon.py

@@ -30,3 +30,44 @@ def go(self, x: int, coins: List[int]) -> int:
         self.dp[x] = mm if mm != 100000 else -1 # memoization
 
         return self.dp[x]
+
+
+
+
+
+
+
+
+# --------
+
+class Solution:
+    def coinChange(self, coins: List[int], amount: int) -> int:
+        memo = {}
+
+
+        for coin in coins:
+            memo[coin] = 1
+    
+        def go(target: int) -> int:            
+            if target < 0:
+                return -1
+            
+            if target in memo:
+                return memo[target]
+        
+            min_val = 10001
+
+            for coin in coins:
+                res = go(target - coin)
+                if res >= 0:
+                    min_val = min(min_val, res)
+
+            memo[target] = (min_val + 1 if min_val != 10001 else -1)
+
+            return memo[target]
+                
+        if amount == 0:
+            return 0
+
+        return go(amount)
+

find-minimum-in-rotated-sorted-array/sangbeenmoon.py

@@ -20,3 +20,25 @@ def findMin(self, nums: List[int]) -> int:
                 right = mid
 
         return nums[left]
+
+# -----------
+
+# TC : O(logN)
+# SC : 1
+
+class Solution:
+    def findMin(self, nums: List[int]) -> int:
+        
+        left = 0
+        right = len(nums) - 1
+        mid = (left + right) // 2
+
+        while left < right:
+            mid = (left + right) // 2
+
+            if nums[mid] > nums[right]:
+                left = mid + 1
+            else:
+                right = mid
+
+        return nums[left]

word-search/sangbeenmoon.py

@@ -34,3 +34,43 @@ def dfs(self, board, word, cx, cy, idx):
                             self.visited[ny][nx] = True
                             self.dfs(board, word, nx, ny, idx + 1)
                             self.visited[ny][nx] = False
+
+
+# ---
+
+class Solution:
+    def exist(self, board: List[List[str]], word: str) -> bool:
+        
+        dx = [0,0,-1,1]
+        dy = [-1,1,0,0]
+
+        x_len , y_len = len(board[0]) , len(board)
+
+        visited = [[False] * x_len for _ in range(y_len)]
+
+        def go(xx: int, yy: int, pos: int) -> bool:
+            
+            if pos >= len(word) - 1:
+                return True
+            
+            for d in range(4):
+                nx = xx + dx[d]
+                ny = yy + dy[d]
+
+                if 0 <= nx and nx < x_len and 0 <= ny and ny < y_len:
+                    if not visited[ny][nx] and board[ny][nx] == word[pos + 1]:
+                        visited[ny][nx] = True
+                        if go(nx,ny,pos+1):
+                            return True
+                        visited[ny][nx] = False
+            return False
+
+        for y in range(y_len):
+            for x in range(x_len):
+                if board[y][x] == word[0]:
+                    visited[y][x] = True
+                    if go(x,y,0):
+                        return True
+                    visited[y][x] = False
+            
+        return False