#encoding=utf-8
"""
求以下矩阵四边元素之和
"""

l = [
     [1,2,3,4,5],
     [1,2,3,4,5],
     [1,2,3,4,5],
     [1,2,3,4,5],
     [1,2,3,4,5]
]
#方法一，坐标法
four_sides_sum=0
for i in range(len(l)):
    for j in range(len(l[i])):
        if i==0:
            four_sides_sum +=l[i][j]
        if i==4:
            four_sides_sum +=l[i][j]
        if i!=0 and i!=4 and j==0:
            four_sides_sum +=l[i][j]
        if i!=0 and i!=4 and j==4:
            four_sides_sum +=l[i][j]
print(four_sides_sum)

#方法二：用整个矩阵减去里面的矩阵
M = [
     [1,2,3,4,5],
     [1,2,3,4,5],
     [1,2,3,4,5],
     [1,2,3,4,5],
     [1,2,3,4,5]
]


insideSum=0
result=0
for i in range(len(M)):
    for j in range(len(M[i])):
        result+=M[i][j]
        if 0<i<4 and 0<j<4:
            insideSum+=M[i][j]
print("四边的元素之和为：",result-insideSum)