함수 nPr()

1 Java[ | ]

Java
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public class MyClass {
    static long nPr(int n, int r){
		if( r > n ) return -1;
		long res = 1;
		for(int i=1; i<=r; i++) res *= n-i+1;
		return res;
	}
	public static void main(String args[]){
		System.out.println(nPr(1,2)); // -1
		System.out.println(nPr(2,2)); // 1
		System.out.println(nPr(3,2)); // 3
		System.out.println(nPr(4,2)); // 12
		System.out.println(nPr(5,2)); // 20
		System.out.println(nPr(7,3)); // 210
		System.out.println(nPr(10,10)); // 3628800
		System.out.println(nPr(100,5)); // 9034502400
		System.out.println(nPr(1000,5)); // 990034950024000
	}
}
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