# -*- coding: UTF-8 -*- 
class ClassGauss(object):

    def __init__(self, a, b):    
        super(ClassGauss, self).__init__()
        self.a = a
        self.b = b
        self.n = len(self.b)

    def max(self, max_i, max_v, i, j):# get max
        a = self.a
        abs_of_a = abs(a[i][j])

        if max_v < abs_of_a:
            max_v = abs_of_a
            max_i = i
        return max_i, max_v

    def swap(self, ai, j):# change line
        a = self.a
        b = self.b
        n = self.n
        for i in range(0, n):
            temp = a[ai][i]
            a[ai][i] = a[j][i]
            a[j][i] = temp

            tempb = b[ai]
            b[ai] = b[j]
            b[j] = tempb

    def gauss(self):
        n = self.n
        max_i = 0 # line num of max value
        max_v = m = self.a[0][0]
        for j in range(0, n-1): 
            for i in range(j, n): 
                max_i, max_v = self.max(max_i, max_v, i, j)
            if max_v == 0:
                raise ValueError('no unique solution')
            if debug:
                print('max_v = %f' % max_v)
                print('max_i = %f , j = %f' % (max_i, j))
            if max_i != j:
                # jiaohuan ai hang he ajhang
                self.swap(max_i, j)
            if debug:
                print('SWAP*******')
                print(self.a)
                print(self.b)
            for p in range(j+1, n):
                l =  a[p][j] / a[j][j]
                # print('l = %f' % (l))
                b[p] -= l * b[j]
                for q in range(j, n):
                    a[p][q] -= l * a[j][q]
            if debug:        
                print('CAL_a******')
                print(self.a)
                print(self.b)
            max_v = m
        if debug:
            print("************************")
            print(self.a)
            print(self.b)
        self.calculate()

    def calculate(self):
        n = self.n - 1
        xn = b[n] / a[n][n]
        print('xn = %f'% xn)
                    
    
   
if __name__ == '__main__':
    # example1
    a = [[0.012, 0.0100, 0.1670],
         [1.000, 0.8334, 5.910],
         [3200, 1200, 4.200]]
    b = [0.6781, 12.10, 983.3]
    debug = False
    # example2
    # a = [[2.00, -4.00, 2.00],[1.00, 2.00, 3.00],[-3.00, -2.00, 5.00]]
    # b = [2.00, 3.00, 1.00]
    g = ClassGauss(a,b)
    g.gauss()