Can someone please provide the editorial of this question.
You are given with integers a, b, c, d, m. These represent the modular equation of a curve y^2 mod\ m = (ax^3+bx^2+cx+d)\ mod\ m
Also, you are provided with an array A of size N. Now, your task is to find the number of pairs in the array that satisfy the given modular equation.
If (A_i, A_j) is a pair then A_j^2\ mod \ m = (aA_i^3+bA_i^2+cA_i+d)\ mod\ m.
Since the answer could be very large output it modulo 10^9 + 7.
Note: A pair is counted different from some other pair if either A_i of the two pairs is different or A_j of the two pairs is different. Also for the convenience of calculations, we may count (A_i, A_j) as a valid pair if it satisfies given constraints.
First line of the input contains number of test cases T.
First line for each test case consists of 5 space-separated integers a, b, c, d, m, corresponding to modular equation given.
Next line contains a single integer N.
Next line contains space-separated integers corresponding to values of array A.
For each test case, output a single line corresponding to number of valid pairs in the array mod 10^9 + 7.
1 \le T \le 10\\ 1 \le N \le10^5\\ -2 \times10^9 \le a,b,c,d,A_i \le 2 \times 10^9\\ 1 \le m \le 2 \times 10^9
1 2 1 -1 3 5 5 10 2 3 14 12
Equation of curve: y^2=2x^3+x^2-x+3 and m = 5.
Valid pairs satisfying equation of line are (x, y) = (2, 14) and (12, 14). Therefore, the answer is 2.
Note: This question is taken from Hackerearth Lenskart hiring challenge which has already expired.