[英]How could I solve this recursion problem with C++
Calculate C (n, k) being:计算 C (n, k) 为:
C (n, 0) = C (n, n) = 1 if n >= 0
C (n, k) = C (n -1, k) + C (n - 1, k - 1) if n > k > 0
I really don't understand very well, I know it is a recursive function that got as arguments n and k variables.我真的不太明白,我知道这是一个递归函数,它作为参数n和k变量。
This is some of what I'd.这是我想要的一些东西。
#include <iostream>
using namespace std;
int calc(int n, int k) {
if (n >= 0) {
return 1;
}
if (n > k > 0) {
return calc(n - 1, k) + calc(n - 1, k - 1);
}
return calc(n, k);
}
int main() {
int n, k;
cout << "Give a number for n: ";
cin >> n;
cout << "Give a number for k: ";
cin >> k;
cout << calc(n, k);
return 0;
}
The first if statement in your function函数中的第一个 if 语句
if (n >= 0) {
return 1;
}
is already wrong because there is no such a condition used in the if statement described in the assignment.已经是错误的,因为在赋值中描述的 if 语句中没有使用这样的条件。
Also the condition in this if statement也是这个 if 语句中的条件
if (n > k > 0)
does not make sense.没有意义。
It seems what you need is the following function definition.看来您需要的是以下函数定义。
#include <iostream>
unsigned long long calc( unsigned int n, unsigned int k )
{
return k == 0 || not( k < n ) ? 1 : calc( n - 1, k ) + calc( n - 1, k - 1 );
}
int main()
{
const unsigned int N = 10;
for ( unsigned int k = 1; k < N; k++ )
{
std::cout << calc( N, k ) << '\n';
}
}
The program output is程序输出是
10
45
120
210
252
210
120
45
10
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