First, the recursive function, the popular saying is that the function itself calls itself ...
such as: N!=n (n-1)!
You define the function f (n) =nf (n-1)
and f (n-1) is the function of this definition. This is recursion.
Second, why use recursion: The purpose of recursion is to simplify the programming, make the program easy to read
Third, the drawback of recursion: although the non-recursive function of high efficiency, but more difficult to program, poor readability. The disadvantage of recursive function is to add the system overhead, that is, each recursive, the stack memory occupies a section more
Iv. conditions of recursion: statements that require completion of a task, need to meet the requirements of recursion (decrease rather than divergence)
V. Advanced recursion:
1. Use recursion to calculate the factorial of N:
Analysis: n!=n* (n-1) * (n-2) ... *
public int Dreturn (int n) {
if (n==1) {
return 1;
}else{
Return N*dreturn (n-1);
}
}
2. Use the recursive function to calculate the sum of 1 to N: 1+2+3+4+. +n
public int Dreturn (int n) {
if (n==1) {
return 1;
}else{
Return N+dreturn (n-1);
}
}
3. Require output a sequence: 1,1,2,3,5,8,11 ... (the sum of the first two digits of each number, requiring a recursive function)
A function is represented by the return of Java: F (n) =f (n-1) +f (n-2); F (0) = 1; F (1) = 1;
Analysis: x1=1; X2=1; x3=x1+x2; x4=x2+x3; ... ; Xn=x (n-1) +x (n-2)
public int F (int n) {
if (n==1) {
return 1;
}else if (n==2) {
return 1;
}else{
Return F (n-1) +f (n-2);
}
}
4.java reverse printing of individual elements in an integer array using a recursive method
public static void printall (int index,int[] arr) {
System.out.println (Arr[index]);
if (Index > 0) {
Printall (--index,arr);
}
}
public static void Main (string[] args) {
Int[] arr={1,2,3,4,5};
Printall (Arr.lenth-1,arr);
}
5. Programming Solution: If a heifer, starting from the birth of the fourth year start a cow, according to the law, how many cows in the nth years?
public static int cattle (int n) {
if (n<=0) {
return 0;
}else if (n<=3) {
return 1;
}else{
Return cattle (n-1) +cattle (n-3);
}
}
public static void Main (string[] args) {
int n=10;
System.out.println (n+ "years later jointly owned" +cattle (n) + "cattle");
}
The concept of recursion, linear recursion, and tail recursion?
