把問題轉換成一個只有0和1的二維陣列，

例如題意轉換為

[0,0,0,0,1,0,0,0,0,0]

[0,0,0,0,0,0,0,1,0,0]

[0,0,1,0,0,0,0,0,0,0]

[0,0,0,0,0,0,0,0,0,1]

[0,0,0,0,0,0,1,0,0,0]

[1,0,0,0,0,0,0,0,0,0]

[0,0,0,0,0,0,0,0,1,0]

[0,1,0,0,0,0,0,0,0,0]

[0,0,0,0,0,1,0,0,0,0]

[0,0,0,1,0,0,0,0,0,0]

其實就是在算有幾個cycle（自己和自己是朋友也是一個cycle）

for all i,i=0~N-1先算A[i][i]有幾個1

再來就是你想的那樣子做，當N非常大的時候會快很多