- https://pintia.cn/problem-sets/12/problems/354
- double fn(double x, int n)
- {
- double ret;
- double item, flag;
- if (n == 1)
- {
- ret = x;
- }
- else
- {
- if (n % 2)
- {
- flag = 1;
- }
- else
- {
- flag = -1;
- }
- item = 1;
- for (int i = 1; i <= n; i++)
- {
- item = item * x;
- }
- item = item * flag;
- ret = fn(x, n - 1) + item;
- }
- return ret;
- }
来源: http://www.bubuko.com/infodetail-3394560.html