Day 7 >> Spiral Matrix II

Author: keshavsingh4522

Diff for: LeetCode/December 2020/Spiral Matrix II.py

@@ -0,0 +1,36 @@
+#https://leetcode.com/explore/challenge/card/december-leetcoding-challenge/569/week-1-december-1st-december-7th/3557/
+class Solution:
+    def generateMatrix(self, n: int) -> List[List[int]]:
+        l=[[i for i in range(1,n+1)] for i in range(n)]
+        k=n
+        for i in range(n//2):
+            if n>1:
+                # diagonal 4*(k-1)
+                if i==0:
+                    l[i+1][i]=4*(k-1)
+                else:
+                    l[i+1][i]=l[i][i-1]+4*(k-1)
+                    # top left-right
+                    for j in range(i,n-i):
+                        l[i][j]=l[i][j-1]+1
+                    # left top-bottom
+                    for j in range(i+1,n-i+1):
+                        l[j][i-1]=l[j-1][i-1]-1
+                    #bottom left-right
+                    for j in range(i,n-i):
+                        l[n-i][j]=l[n-i][j-1]-1
+                    # right top-bottom
+                    for j in range(i,n-i+1):
+                        l[j][n-i]=l[j-1][n-i]+1
+            
+                k-=2
+        if n>1:
+            if n%2:
+                l[n//2][n//2]=l[n//2][n//2-1]+1
+                l[n//2][n//2+1]=l[n//2-1][n//2+1]+1
+                l[n//2+1][n//2-1]=l[n//2][n//2-1]-1
+                l[n//2+1][n//2]=l[n//2+1][n//2-1]-1
+                l[n//2+1][n//2+1]=l[n//2+1][n//2]-1
+            else:
+                l[n//2][n//2]=l[n//2][n//2-1]-1
+        return l