Create largest-1-bordered-square.py

Author: kamyu104

Python/largest-1-bordered-square.py

@@ -0,0 +1,27 @@
+# Time:  O(n^3)
+# Space: O(n^2)
+
+class Solution(object):
+    def largest1BorderedSquare(self, grid):
+        """
+        :type grid: List[List[int]]
+        :rtype: int
+        """
+        top, left = [a[:] for a in grid], [a[:] for a in grid]
+        for i in xrange(len(grid)):
+            for j in xrange(len(grid[0])):
+                if not grid[i][j]:
+                    continue
+                if i:
+                    top[i][j] = top[i-1][j] + 1
+                if j:
+                    left[i][j] = left[i][j-1] + 1
+        for l in reversed(xrange(1, min(len(grid), len(grid[0]))+1)):
+            for i in xrange(len(grid)-l+1):
+                for j in xrange(len(grid[0])-l+1):
+                    if min(top[i+l-1][j],
+                           top[i+l-1][j+l-1],
+                           left[i][j+l-1],
+                           left[i+l-1][j+l-1]) >= l:
+                        return l*l
+        return 0