What is recursion in java

What is recursion

Recursion as an algorithm is widely used in programming languages. It refers to the function/process/subprogram that directly or Reentrancy caused by indirectly calling itself.

Recursive algorithms are generally used to solve three types of problems:

a. The definition of data is recursively defined. (Fibonacci (Fibonacci) function)

b. The problem solution is implemented by a recursive algorithm. (Traceback)

c. The structural form of data is defined recursively. (Tree traversal, graph search)

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Example:

This is an example of arrangement, What it does is sort all the elements in an input string and output

. For example: if the parameter you give is "abc", the program will output: abc acb bac bca cab cba a

The exit of the algorithm is: low=high, that is, when there is only one arrangement element given now.

The approximation process of the algorithm: first determine the first element of the arrangement, which is the element represented by i in the loop, then low+1 starts to reduce the arrangement elements, and so on, until low=high

Examples are as follows:

public class Foo {
    public static void main(String[] args) {
        permute(“abc”);
    }
    public static void permute(String str) {
        char[] strArray = str.toCharArray();
        permute(strArray, 0, strArray.length – 1);
    }
    public static void permute(char[] list, int low, int high) {
    int i;
    if (low == high) {
        String cout = “”;
        for (i = 0; i <= high; i++){
            cout += list[i];
        System.out.println(cout);
        }
    }else {
    for (i = low; i <= high; i++) {
        char temp = list[low];
        list[low] = list[i];
        list[i] = temp;
        permute(list, low + 1, high);
        temp = list[low];
        list[low] = list[i];
        list[i] = temp;
    }
    }
    }
}

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