用于 C/C++ 中的模方程解的程序?
在这里,我们将看到一个与模方程有关的有趣问题。假设我们有两个值 A 和 B。我们必须找到变量 X 可以采用的可能值数,使得 (A mod X) = B 成立。
假设 A 为 26,B 为 2。那么 X 的首选值将是 {3, 4, 6, 8, 12, 24}。因此,计数将为 6。这就是答案。让我们看看算法以获得更好的理解。
算法
possibleWayCount(a, b) −
begin if a = b, then there are infinite solutions if a < b, then there are no solutions otherwise div_count := find_div(a, b) return div_count end
find_div(a, b) −
begin n := a – b div_count := 0 for i in range 1 to square root of n, do if n mode i is 0, then if i > b, then increase div_count by 1 end if if n / i is not same as i and (n / i) > b, then increase div_count by 1 end if end if done end
示例
#include <iostream> #include <cmath> using namespace std; int findDivisors(int A, int B) { int N = (A - B); int div_count = 0; for (int i = 1; i <= sqrt(N); i++) { if ((N % i) == 0) { if (i > B) div_count++; if ((N / i) != i && (N / i) > B) //ignore if it is already counted div_count++; } } return div_count; } int possibleWayCount(int A, int B) { if (A == B) //if they are same, there are infinity solutions return -1; if (A < B) //if A < B, then there are two possible solutions return 0; int div_count = 0; div_count = findDivisors(A, B); return div_count; } void possibleWay(int A, int B) { int sol = possibleWayCount(A, B); if (sol == -1) cout << "For A: " << A << " and B: " << B << ", X can take infinite values greater than " << A; else cout << "For A: " << A << " and B: " << B << ", X can take " << sol << " values"; } int main() { int A = 26, B = 2; possibleWay(A, B); }
输出
For A: 26 and B: 2, X can take 6 values
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