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;}