1209. Sequence Sum Possibi

TAG 数论

简单的数学题。设 n+.. +(n+k)=X， n>0,k>0

有 (2n+k)(k+1)=2X

k(k+1) <2X

k^2<2X

k<sqrt(2X)

枚举k到sqrt(2X)就行了

/* source code of submission 421009, Zhongshan University Online Judge System */
#include <stdio.h>
#include <math.h>
int T; 
int no,n;
int cal(int n)
{
    int ret=0;
    for (int i=1; i<=int( sqrt(2.0)*sqrt(n+0.0) ); ++i)
    {
        if ( (2*n)%(i+1)==0  && (2*n/(i+1)-i) >=2 && (2*n/(i+1)-i)%2==0 )
        {
            ++ret;
        }
    }
    return ret;
}
int main(int argc, char *argv[])
{
    scanf("%d", &T);
    while ( T-- )
    {
        scanf("%d%d", &no, &n);
        printf("%d %d/n",no, cal(n) );
    }
    return 0;
}