[ppxyn1] WEEK 06 solutions

container-with-most-water/ppxyn1.py

@@ -0,0 +1,15 @@
+# idea : two-pointer
+class Solution:
+    def maxArea(self, height: List[int]) -> int:
+        max_area = 0
+        start, end = 0, len(height) - 1
+        while start < end:
+            area = (end - start) * min(height[start], height[end])
+            max_area = max(max_area, area)
+            if height[start] < height[end]:
+                start += 1
+            else:
+                end -= 1
+        return max_area
+
+

longest-increasing-subsequence/ppxyn1.py

@@ -0,0 +1,13 @@
+# idea: DP 
+# O(N^2)
+class Solution:
+    def lengthOfLIS(self, nums: List[int]) -> int:
+        LIS = [1] * len(nums)
+        for i in range(len(nums) - 1, -1, -1):
+            for j in range(i+1, len(nums)):
+                if nums[i] < nums[j]:
+                    LIS[i] = max(LIS[i], 1+LIS[j])
+        return max(LIS)
+
+
+

spiral-matrix/ppxyn1.py

@@ -0,0 +1,34 @@
+# idea : -
+# O(m*n)
+class Solution:
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        res = []
+        left, right = 0, len(matrix[0])
+        top, bottom = 0, len(matrix)
+
+        while left < right and top < bottom:
+            # get every i in the top row
+            for i in range(left, right):
+                res.append(matrix[top][i])
+            top+=1
+
+            # get every i in the right col
+            for i in range(top, bottom):
+                res.append(matrix[i][right - 1])
+            right -= 1
+
+            if not (left < right and top < bottom):
+                break
+            #get every i in the bottom row
+            for i in range(right - 1, left - 1, -1):
+                res.append(matrix[bottom-1][i])
+            bottom -= 1
+
+            # get every i in the left col 
+            for i in range(bottom -1, top-1, -1):
+                res.append(matrix[i][left])
+            left += 1
+        return res
+
+
+

valid-parentheses/ppxyn1.py

@@ -0,0 +1,22 @@
+# idea : stack
+
+class Solution:
+    def isValid(self, s: str) -> bool:
+        mapping = {"(": ")", "{": "}", "[": "]"}
+        stack = []
+
+        for ch in s:
+            if ch in mapping:
+                stack.append(ch)
+            else:
+                if not stack:
+                    return False
+                if mapping[stack.pop()] != ch:
+                    return False
+        if stack:
+            return False
+
+        return True
+
+
+