poj2249 2010.2.8

poj2249 2010.2.8

#include <stdio.h>
#include <string.h>

int cm(int,int);

int cm(int n,int m)
{
//	printf("%d %d\n",n,m); 
	if ((m==0)||(n==m)) return 1;
	if (m==1) return n;
	return (cm(n-1,m)+cm(n-1,m-1));
}

void main()
{
	int n1,m1;
	while (scanf("%d %d",&n1,&m1),n1)
		printf("%d\n",cm(n1,m1));
}


记忆化


#include <stdio.h>

long long result[200][200];

long long c (long long m, long long n) {
    long long s;

    if (m < 200 && n < 200 && result[m][n]) return result[m][n];

    if (n == 0 || n == m) s = 1;
    else if (n == 1 || n == m - 1) s = m;
    else if (n > m - n) s = c (m, m - n);
    else s = m * c (m - 1, n - 1) / n;
    if (m < 200 && n < 200) result[m][n] = s;
    return s;
}

int main ()
{
    long long m, n;
    while (scanf ("%lld %lld", &m, &n) && (m || n)) {
        printf ("%lld\n", c (m, n));
    }

    return 0;
}