Recursion: don't understand this result

Question

void func(int num){
    if(num< 3){
        printf("%d ", num);
        func(num+ 1);
        printf("%d ", num);
    }
}

Suppose I call this function with func(0). Why is the result 0 1 2 2 1 0 ? I don't know why it's decreasing.

Answer 1

Here's a stack trace

f(0)
    print 0
    f(1)
        print 1
        f(2)
            print 2
            f(3)  // 3 < 3 == false
            print 2
         print 1
     print 0