15. C # Basic Collation (Recursive)

Functions with output parameters

An input parameter is equivalent to a function, which is equivalent to a variable that has already been assigned and is directly available
The output parameter is equivalent to defining a variable without a value, assigning it in a function, and then calling the function to take the assignment out of the function

Cases:

 Public void Shuchu (intoutint  b) {   ten//B must be assigned }

The notation inside the main function:

Static void Main (string[] args) {intNew program ();p. Shuchu (A,   out B); // b needs to be defined first, corresponding to the data type of the function, to receive the data passed out Console.WriteLine (b); // +}

Exercise: Write a two-time equation solution with output parameters (returns whether there is a solution, and the value of X1,X2)

 Public stringFangcheng (intAintBintC out DoubleX1, out Doublex2) {            DoubleDe = (Double) b * B-4AC; if(A = =0) {x1= x2 =-1; return "not a unary two-time equation ."; }            Else if(De <0) {x1= x2 =-1; return "de<0, this equation has no solution"; }            Else{x1= (Double) (-B + de)/2*A; X2= (Double) (-B-DE)/2*A; return "have a solution"; }        }

AnswerRecursive

First, the concept:

The function body calls the function itself until a condition is met and no further calls are continued.

* * Simply let the function perform the first step to meet the condition and then start calling the function itself with the data.

Second, should meet the conditions:

(1) There is a process of repeated execution (call itself);

(2) There are conditions for jumping out of the process of repeated execution (function exit)

Iii. examples

Calculation of factorial n! = N (n-1) * (n-2) * (n-3) *......*1 (n>0)

Iv. Precautions Notice:

1. There must be a loop-over condition in the recursion.

2, each call of the recursive function needs the stack to store, if the number of times too many words easily cause stack overflow.

Practice:

1, n peach, every day eat 1/2+1, 7 days left one, there are a few peach?

 Public int tao (int day  )        {            if7)            {                return  1;            }             int 1) +1) *2;             return sum;        }

Answer

2, a person to drive a flock of sheep to sell, every village sold 1/3+1 only, 7 villages left 2, there are a few sheep?

 Public Double Yang (int  cun)        {            if7)            {                return  2;            }             double sum = (double113;             return sum;        }

Answer

15. C # Basic Collation (Recursive)