Repository navigation
Expand file tree
/
Copy path064.最小路径和.py
More file actions
52 lines (47 loc) · 1.75 KB
/
Copy path064.最小路径和.py
File metadata and controls
52 lines (47 loc) · 1.75 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
# 动态规划，dp记录每个位置的最短路径
# 状态转移方程 dp[i][j] = min(dp[i-1][j], dp[i][j-1]) + grid[i][j]
class Solution(object):
def minPathSum(self, grid):
m, n = len(grid), len(grid[0])
dp = [[0]*n]*m
for i in range(m):
for j in range(n):
if i == 0 and j == 0:
dp[i][j] = grid[i][j]
elif i == 0 and j != 0:
dp[i][j] = dp[i][j-1] + grid[i][j]
elif i != 0 and j == 0:
dp[i][j] = dp[i-1][j] + grid[i][j]
else:
dp[i][j] = min(dp[i-1][j], dp[i][j-1]) + grid[i][j]
return dp[-1][-1]
# 原地修改
class Solution2(object):
def minPathSum(self, grid):
for i in range(len(grid)):
for j in range(len(grid[0])):
if i == 0 and j == 0:
continue
elif i == 0 and j != 0:
grid[i][j] += grid[i][j-1]
elif i != 0 and j == 0:
grid[i][j] += grid[i-1][j]
else:
grid[i][j] += min(grid[i-1][j], grid[i][j-1])
return grid[-1][-1]
# 动态规划经典写法
class Solution(object):
def minPathSum(self, grid):
m, n = len(grid), len(grid[0])
dp = [[0]*n for _ in range(m)]
dp[0][0] = grid[0][0]
# 初始化首行首列
for i in range(1, m):
dp[i][0] = dp[i-1][0] + grid[i][0]
for j in range(1, n):
dp[0][j] = dp[0][j-1] + grid[0][j]
# 遍历每个位置
for i in range(1, m):
for j in range(1, n):
dp[i][j] = min(dp[i-1][j], dp[i][j-1]) + grid[i][j]
return dp[-1][-1]