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  1. def numPaths(warehouse):
  2.     MOD = 10**9 + 7
  3.  
  4.     # Handle edge case for an empty grid
  5.     if not warehouse or not warehouse[0]:
  6.         return 0
  7.  
  8.     n = len(warehouse)
  9.     m = len(warehouse[0])
  10.  
  11.     # If the starting or ending cell is blocked, no path is possible
  12.     if warehouse[0][0] == 0 or warehouse[n-1][m-1] == 0:
  13.         return 0
  14.  
  15.     # Create a 1D DP array to track paths for the current row
  16.     dp = [0] * m
  17.     dp[0] = 1 # Start position has 1 path
  18.  
  19.     for i in range(n):
  20.         for j in range(m):
  21.             if warehouse[i][j] == 0:
  22.                 # If the cell is blocked, ways to reach it drop to 0
  23.                 dp[j] = 0
  24.             elif j > 0:
  25.                 # dp[j] currently holds the value from the top cell (i-1, j)
  26.                 # dp[j-1] holds the value from the left cell (i, j-1)
  27.                 dp[j] = (dp[j] + dp[j-1]) % MOD
  28.  
  29.     # The last element contains the paths to the bottom-right corner
  30.     return dp[m-1]
  31.  
  32. print(numPaths([[1,1,1,1],[1,1,1,1],[1,1,1,1]]))
Success #stdin #stdout 0.1s 14052KB
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https://ideone.com/gH1QWG
language:
Python 3 (python  3.12)
created:
3 hours ago
visibility:
public

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