本题要求实现一个用递归计算1+2+3+…+n的和的简单函数。 函数接口定义： int sum( int n ); 该函数对于传入的正整数n返回1+2+3+…+n的和；若n不是正整数则返回0。题目保证输入输出在长整型范围内。建议尝试写成递归函数

FJ is about to take his N (1 ≤ N ≤ 2,000) cows to the annual"Farmer of the Year" competition. In this contest every farmer arranges his cows in a line and herds them past the judges. The contest organizers adopted a new registration scheme this year

补充了猴子吃桃的递归写法