题解 | 二维斐波那契数列

# a[1][1]=1
# a[2][1]=a[1][1]=1
# a[3][1]=a[2][1]=1

# a[1][2]=a[1][1]=1
# a[1][3]=a[1]a[2]=1

# a[2][2]=a[1][2]+a[2][1]=1+1=2
# a[2][3]=a[1][2]+a[2][2]=1+2=3
#参考，第一行和第一列都是1
n, m = map(int, input().split())
a = [[0] * (m + 1) for _ in range(n + 1)]
for i in range(1, n + 1):
    a[i][1] = 1
for j in range(1, m + 1):
    a[1][j] = 1
for i in range(2, n + 1):
    for j in range(2, m + 1):
        a[i][j] = a[i-1][j] + a[i][j-1]

result = a[n][m] % (10**9 + 7)
print(result)