c语言程序求答案和解析

Question

#include<stdio.h>double f(double x,double y){if(x>=y)return (x+y)/2.0;else return f(f(x+2,y-1),f(x+1,y-2));}void main (){printf ("%.1f",f(5.0,7.0));}

Answer 1

应该是6.0