# C 程序：計算并打印 nPr 的值 > 原文： [https://beginnersbook.com/2015/02/c-program-to-calculate-and-print-the-value-of-npr/](https://beginnersbook.com/2015/02/c-program-to-calculate-and-print-the-value-of-npr/) 在下面的程序中，我們根據給定的`n`和`r`值計算 nPr 的值。 nPr 也可以表示為`P(n, r)`。`P(n, r)`的公式是`n! /(n - r)!`，例如 `P(6, 2)= 6! /(6-2)! => 720/24 = 30`。我們在下面的 C 程序中實現了相同的邏輯。 ```c #include <stdio.h> void main() { int n, r, npr_var; printf("Enter the value of n:"); scanf("%d", &n); printf("\nEnter the value of r:"); scanf("%d", &r); /* nPr is also known as P(n,r), the formula is: * P(n,r) = n! / (n - r)! For 0 <= r <= n. */ npr_var = fact(n) / fact(n - r); printf("\nThe value of P(%d,%d) is: %d",n,r,npr_var); } // Function for calculating factorial int fact(int num) { int k = 1, i; // factorial of 0 is 1 if (num == 0) { return(k); } else { for (i = 1; i <= num; i++) { k = k * i; } } return(k); } ``` **輸出：** ```c Enter the value of n: 5 Enter the value of r: 2 The value of P(6,2) is: 30 ```