unique-paths-ii.go

package problem0063

func uniquePathsWithObstacles(obstacleGrid [][]int) int {
	m := len(obstacleGrid)
	if m == 0 {
		return 0
	}

	n := len(obstacleGrid[0])
	if n == 0 {
		return 0
	}
	
	dp := make([][]int, m)
	for i := range dp {
		dp[i] = make([]int, n)
	}

	if obstacleGrid[0][0] == 0 {
		dp[0][0] = 1
	}

	for i := 1; i < m; i++ {
		if obstacleGrid[i][0] == 0 {
			dp[i][0] = dp[i-1][0]
		}
	}

	for j := 1; j < n; j++ {
		if obstacleGrid[0][j] == 0 {
			dp[0][j] = dp[0][j-1]
		}
	}

	for i := 1; i < m; i++ {
		for j := 1; j < n; j++ {
			if obstacleGrid[i][j] == 0 {
				dp[i][j] = dp[i-1][j] + dp[i][j-1]
			}
		}
	}

	return dp[m-1][n-1]
}