df

228-15.py

@@ -39,9 +39,30 @@ def Inverse(A):
         return None
     A_inv = [[B[i][j] / det for j in range(n)] for i in range(n)]
     return A_inv
+
+
+def FixInv(A):
+    n = len(A)
+    if n == 2:
+        return [[A[1][1] / Det(A), -A[0][1] / Det(A)],
+                [-A[1][0] / Det(A), A[0][0] / Det(A)]]
+    B = [[0 for i in range(n)] for j in range(n)]
+    for i in range(n):
+        for j in range(n):
+            t = [row[:j] + row[j+1:] for row in (A[:i] + A[i+1:])]
+            B[j][i] = ((-1) ** (i + j)) * Det(t)
+    det = Det(A)
+    if det == 0:
+        print("矩阵不可逆")
+        return None
+    A_inv = [[B[i][j] / det for j in range(n)] for i in range(n)]
+    return A_inv
+
+
 # 计算矩阵的条件数
 def Cond(A,v):
-    inv_A = Inverse(A)
+    # inv_A = Inverse(A)
+    inv_A = FixInv(A)
     print(inv_A,Norm(A, v), Norm(inv_A, v))
     return Norm(A, v) * Norm(inv_A, v)