# Find the Surface area of a 3D figure in Python

PythonServer Side ProgrammingProgramming

Suppose we have a N*M matrix A, this is the representation of 3D figure. The height of the building at point (i, j) is A[i][j]. We have to find the surface area of the figure.

So, if the input is like N = 3, M = 3, A = [[1, 4, 5],[3, 3, 4],[1, 3, 5]], then the output will be 72.

To solve this, we will follow these steps −

• res := 0

• for i in range 0 to N, do

• for j in range 0 to M, do

• up_side := 0

• left_side := 0

• if i > 0, then

• up_side := array[i - 1, j]

• if j > 0, then

• left_side := array[i, j - 1]

• res := res + |array[i][j] - up_side| + |array[i][j] - left_side|

• if i is same as N - 1, then

• res := res + array[i, j]

• if j is same as M - 1, then

• res := res + array[i, j]

• res := res + N * M * 2

• return res

## Example

Let us see the following implementation to get better understanding −

Live Demo

M = 3
N = 3
def get_surface_area(array):
res = 0
for i in range(N):
for j in range(M):
up_side = 0
left_side = 0
if (i > 0):
up_side = array[i - 1][j]
if (j > 0):
left_side = array[i][j - 1]
res += abs(array[i][j] - up_side)+abs(array[i][j] - left_side)
if (i == N - 1):
res += array[i][j]
if (j == M - 1):
res += array[i][j]
res += N * M * 2
return res
array = [[1, 4, 5],[3, 3, 4],[1, 3, 5]]
print(get_surface_area(array))

## Input

[[1, 4, 5],[3, 3, 4],[1, 3, 5]]

## Output

72