PKU 2000. Gold Coins. [판정:AC]

역시 -_-; 이건 쉬운문제였군요 -_-ㅋ

군수열을 응용하면 간단하게 풀립니다 :)

#include <stdio.h> int dscanf( int *pnum ) { scanf("%d", pnum); return *pnum; } int sigma_k( int n ) { return n * (n+1) / 2; } int sigma_ksquare( int n ) { return n * (n+1) * (2*n+1) / 6; } void main() { int day; int temp, i; while( dscanf(&day) != 0 ) { i = 0; do { i++; temp = sigma_k(i); } while( day >= temp ); i--; temp = sigma_k(i); if( day == temp ) { printf("%d %d\n", day, sigma_ksquare(i)); } else { int day_diff = day - temp; printf("%d %d\n", day, sigma_ksquare(i) + day_diff * (i+1)); } } }