Array-1

DiagonalTraversal.py

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+# Time Complexity --> O(m*n)
+# Space Complexity --> O(1). There is no auxillary space
+# Approach --> We traverse through the matrix in such a way that at each boundary, we create rules that change the direction and the way we tranverse to next within bounds element
+class Solution:
+    def findDiagonalOrder(self, mat: List[List[int]]) -> List[int]:
+        m = len(mat)
+        n = len(mat[0])
+
+        i = 0
+        j = 0
+        re = [0]*(m*n)
+        upflag = 1
+        for k in range(m*n):
+            re[k] = mat[i][j]
+            if upflag==1:
+                if j==n-1:
+                    i = i+1
+                    upflag = 0
+                elif i==0:
+                    j = j+1
+                    upflag = 0
+                else:
+                    i = i-1
+                    j = j+1
+            else:
+                if i==m-1:
+                    j = j+1
+                    upflag = 1
+                elif j==0:
+                    i = i+1
+                    upflag = 1
+                else:
+                    i = i+1
+                    j = j-1
+        return re
+

ProductOfArrayExceptSelf.py

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+# Time Complexity --> O(n)
+# Space Complexity --> O(1) There is no auxillary space
+# Approach --> At each index, we find the running product to the left and right of it individually and then produce the result using their product.
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        answer = []
+        # Find the running prod to the left of each element
+        lprod = 1
+        answer.append(lprod)
+        for i in range(1, len(nums)):
+            lprod = lprod * nums[i-1]
+            answer.append(lprod)
+
+        rprod = 1
+        for i in range(len(nums)-2,-1,-1):
+            rprod = rprod * nums[i+1]
+            answer[i] = answer[i]*rprod
+        return answer 
+
+
+'''
+# Time Complexity --> O(n*2)
+# Space Complexity --> O(1) There is no auxillary space
+class Solution:
+    def productExceptSelf(self, nums: List[int]) -> List[int]:
+        answer = []
+        for i in range(len(nums)):
+            prod = 1
+            for j in range(len(nums)):
+                if i!=j:
+                    prod = prod*nums[j]
+            answer.append(prod)
+        return answer 
+
+'''

SpiralMatrix.py

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+# Time Complexity --> O(m*n)
+# Space Complexity --> O(1) as there is no auxillary space utilized
+# Approach --> We start off with boundaries on 4 sides of the matrix and as we traverse through a row or a column, we manipulate the boundary values to avoid traversing the same elements. 
+class Solution:
+    def spiralOrder(self, matrix: List[List[int]]) -> List[int]:
+        m = len(matrix)
+        n = len(matrix[0])
+        top, bottom = 0, m-1
+        left, right = 0, n-1
+
+        re = []
+        while top<=bottom and left<=right:
+            # left to right
+            for j in range(left, right+1):
+                re.append(matrix[top][j])
+            top = top+1
+
+            # top to bottom
+            for i in range(top, bottom+1):
+                re.append(matrix[i][right])
+            right = right-1
+
+            if top<=bottom:
+                # right to left
+                for j in range(right, left-1, -1):
+                    re.append(matrix[bottom][j])
+                bottom = bottom-1
+
+            if left<=right:
+                # bottom to top
+                for i in range(bottom, top-1, -1):
+                    re.append(matrix[i][left])
+                left = left+1
+
+        return re