Created
December 16, 2018 01:05
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Implementation of the Jacobi symbol
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| _s2 = {1:1, 3:-1, 5:-1, 7:1} | |
| def jacobi(a,n): | |
| a = a % n | |
| assert(a) | |
| res = 1 | |
| while not a&1: | |
| res *= _s2[n % 8] | |
| a = a//2 | |
| if a == 1: | |
| return res | |
| if n%4 == 3 and a%4 == 3: | |
| res = -res | |
| return res * jacobi(n, a) |
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