How to implement Java binary search using recursive algorithm

How to implement the recursive algorithm of binary search in java

public class Binary recursive search {

public static void main(String[] args) is the entry point of the Java program and the starting position of program execution. In this method, the main logic and functionality of the program can be written. This method must be defined in a specific format before it can be called and executed by the Java virtual machine. In the parameter list of the main method, args is a string array that can be used to receive command line parameters. By writing code in the main method, we can implement various functions, such as printout, calculation, loop, conditional judgment, etc. {

//Define the array. Note that the binary search array must be an ordered array!

int[] arr = { 1, 3, 5, 7, 9, 11, 13, 15, 17 }; is the declaration and initialization statement of an integer array, which contains 9 elements. The value of each element is 1, 3, 5, 7, 9, 11, 13, 15, 17. In this way, we create an integer array named arr and assign it an initial value. In subsequent programs, we can use this array to perform various operations, such as searching, sorting, and counting

//Accept the return value after the search: index value, if not, it is -1;

//Test search element: 9

int a = binarySearch(arr, 9, 0, arr.length - 1);

System.out.println("The index position of the number being searched is: " a);

}

//The parameter list is: the array to be searched, the number to search for, the head index, and the tail index!

public static int binary(int[] arr, int key, int start, int end) // Recursion

{

//Create every time you come in, the intermediate index value!

int mid = (star end) / 2;

If the number to be searched is less than the starting index or greater than the ending index, or the starting index is greater than the ending index, it means that the number does not exist and -1 is returned.

if (key arr[end] || start > end) {

return -1;

}

//If the middle value is less than the number being searched, redefine the header index and move it to the middle 1 position, so that half of the numbers can be filtered out!

if (arr[mid]

//Start recursion!

return binary(arr, key, mid 1, end); // Continue binary search in the second half of the array

//Otherwise, if the middle value is greater than the number being searched, move the tail index back to the middle position of -1, so that half of the numbers can be filtered out!

} else if (arr[mid] > key) {

//Start recursion!

return binary(arr, key, start, mid - 1);

} else {

//If not, it is found and returns to the index!

return mid;

}

}

}

Master programming JAVA language uses recursive algorithm and 1 2 3 4 100 or 11 13 15

first question:

public class CalSum {

public static void main(String[] args) is the entry point of the Java program and the starting position of program execution. In this method, the main logic and functionality of the program can be written. This method must be defined in a specific format before it can be called and executed by the Java virtual machine. In the parameter list of the main method, args is a string array that can be used to receive command line parameters. By writing code in the main method, we can implement a variety of functions, such as printout, calculation, looping, conditional judgment, etc.

{

CalSum calSum = new CalSum();

int result = calSum.calculate(100); // Call the calculate method of the calSum object, pass in the parameter 100, and assign the result to the result variable.

System.out.println("The sum of 1 2 3 ... 100 is equal to" result);

}

public int calculate(int number)

{

int result = 0;

if(number == 1)

{

result = 1;

}

else

{

result = number calculate(number - 1); The result is to add the current number and the return value of number-1. This expression can be calculated recursively. Each time the recursive call is made, the value of number will be decremented by 1 until the recursion stops when number equals 1. The return value of the recursive call will be continuously accumulated into the final result. In this way, we can get the sum of a sequence.

}

return result;

}

}

What are the algorithms of recursion and iteration in java

Iteration is an ordinary loop.

Example: Add from 1 to 10

int sum=0

for(int i=0;i

sum=sum i;

}

Recursion means that a function calls itself directly or indirectly.

For example: Once upon a time there was a big monk and a little monk in a temple. The big monk asked the little monk to tell a story. The little monk said that once upon a time there was a big monk and a little monk in a temple. The little monk asked the big monk to tell a story. In the story, the big monk went on to say that once upon a time there was a big monk and a little monk in a temple. They practiced and studied Buddhism together every day.

Characteristics of recursion:

There must be three conditions:

1. Call yourself indirectly or directly.

2. When playing the game, be sure to set conditions for exiting. For example, the great monk will stop listening to the story if his mouth is dry. If exit conditions are not set, the game may fall into an infinite loop.

3. There must be a logical body (what you want to do);

public int sum(int x){

if(x

return x;

}

return x sum(x-1);

}

int s=10;

int total=sum(s);

In this example, the sum function always calls itself, return x sum(x-1);

sum has exit conditions, x

The final result is to return 10 9 8 7 ... 1

In many cases, both iteration and recursion can achieve the same function, but there are some functions that iteration cannot complete. In addition, recursive code is more concise, and proficient use of recursion can improve code quality.

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