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// Dart function to calculate factorial
int factorial(int n) {
if (n <= 0) {
return 1;
}
return n * factorial(n - 1);
}
// Dart function to calculate permutations
int permutations(int n, int r) {
if (n < r) {
return 0;
}
return factorial(n) ~/ factorial(n - r);
}
// Dart function to calculate combinations
int combinations(int n, int r) {
if (n < r) {
return 0;
}
return factorial(n) ~/ (factorial(r) * factorial(n - r));
}
void main() {
// Example usage
print("Permutations of 5 choose 3: ${permutations(5, 3)}");
print("Combinations of 5 choose 3: ${combinations(5, 3)}");
}