leetcode62. Unique Paths

这个题用组合数学的方法非常简单，我还见过更难一点的，但既然说了要用动态规划，就用动态规划吧

path1

class Solution(object):
    def uniquePaths(self, m, n):
    path=[]
    for i in range(0,m):
    l=[]
    l.append(1)
    path.append(l)


    for i in range(m):
    for j in range(1,n):
    sum=0
    if i==0:
    sum=path[i][j-1]
    else:
    sum=path[i-1][j]+path[i][j-1]
    path[i].append(sum)
    return path[m-1][n-1]

path2

class Solution(object):
    def uniquePathsWithObstacles(self, obstacleGrid):
    m=len(obstacleGrid)
    n=len(obstacleGrid[0])
    path=[]
    f=1
    for i in range(0,m):
    l=[]
    if(obstacleGrid[i][0]==1):
    f=0
    l.append(f)
    path.append(l)
    for i in range(m):
    for j in range(1,n):
    sum=0
    if obstacleGrid[i][j]==1:
    sum=0
    else:
    if i==0 and j==0:
    sum=1
    else:
    if i==0:
    sum=path[i][j-1]
    else:
    if j==0:
    sum=path[i-1][j]
    else:
       sum=path[i-1][j]+path[i][j-1]
    path[i].append(sum)
    return path[m-1][n-1]