题解 | #牛牛学数列#
牛牛学数列
https://www.nowcoder.com/practice/0b97367cd2184c12a0e02f7c223aee11
#include <stdio.h> int main() { int a = 0; int flag = 1;//设置一个标志 scanf("%d",&a); int i = 0; int sum = 0; for(i = 1;i<=a;i++) { sum +=flag*i; flag = -flag;//奇数为正,偶为负 } printf("%d",sum); return 0; }