Python实现行列式计算

# 逆序数
def getInversion(numlist):
count = 0
for i in range(1,len(numlist)):
subscript = numlist[i]
for j in range(i):
if subscript < numlist[j]:
count += 1
return count
D = 0
# 全排列，求每项的积
def permutation(dd,ilist,jlist,index):
global D
for i in range(index,len(jlist)):
if index == len(jlist)-1:
term = 1
for ii in range(len(ilist)):
i = ilist[ii]
j = jlist[ii]
term *= dd[i][j]
if getInversion(jlist) % 2 == 0:
D += term
else:D -= term
return
tmp = jlist[index]
jlist[index] = jlist[i]
jlist[i] = tmp
permutation(dd,ilist,jlist,index+1)
tmp = jlist[index]
jlist[index] = jlist[i]
jlist[i] = tmpif __name__ == '__main__':
dd = [[1, 2, -4], [-2, 2, 1], [-3, 4, -2]]
dd =[[1,1,1,1],[-1,2,1,3],[1,4,1,9],[-1,8,1,27]]
jlist = []
ilist = []
for ii in range(len(dd)):
ilist.append(ii)
jlist.append(ii)
permutation(dd,ilist,jlist,0)
print(D)