C) 백준 5341번 : Pyramids

https://www.acmicpc.net/problem/5341

5341번: Pyramids

 

문제

A pyramid of blocks is constructed by first building a base layer of n blocks and then adding n-1 blocks to the next layer. This process is repeated until the top layer only has one block.

 

pyramids

 

You must calculate the number of blocks needed to construct a pyramid given the size of the base. For example, a pyramid that has a base of size 4 will need a total of 10 blocks.

입력

The input will be a sequence of integers, one per line. The end of input will be signaled by the integer 0, and does not represent the base of a pyramid. All integers, other than the last (zero), are positive.

 

출력

For each positive integer print the total number of blocks needed to build the pyramid with the specified base.

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코드

#include <stdio.h>

int main() {
    int n;
    while (1)
    {
      scanf("%d", &n);

      if (n == 0)
      {
        break;
      }

      int sum = n * (n+1) / 2;
      printf("%d\n", sum);
      
    }
    

    return 0;
}

 

등차수열을 이용하면 된다.