Generate all permutations and combinations of strings through JavaScript functions-JS Tutorial-php.cn

Generate all permutations and combinations of strings through JavaScript functions

藏色散人

Release： 2021-08-03 14:52:13

Original

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Today I will introduce to you how to generate all permutations and combinations of strings through a JavaScript function. The so-called permutations and combinations are the most basic concepts in combinatorics.

First of all, let me give you a brief introduction to permutations and combinations:

1. Arrangement refers to sorting out a specified number of elements from a given number of elements.

2. Combination refers to taking out only a specified number of elements from a given number of elements, regardless of sorting.

The central problem of permutations and combinations is to study the total number of possible situations in permutations and combinations of specified requirements.

I believe everyone has some understanding of permutations and combinations.

Below we will use javascript code to calculate all permutations and combinations of strings.

The complete code is as follows:

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    //编写一个JavaScript函数来生成字符串的所有组合
 function substrings(str1)
    {
        var array1 = [];
        for (var x = 0, y=1; x < str1.length; x++,y++)
        {
            array1[x]=str1.substring(x, y);
        }
        var combi = [];
        var temp= "";
        var slent = Math.pow(2, array1.length);

        for (var i = 0; i < slent ; i++)
        {
            temp= "";
            for (var j=0;j<array1.length;j++) {
                if ((i & Math.pow(2,j))){
                    temp += array1[j];
                }
            }
            if (temp !== "")
            {
                combi.push(temp);
            }
        }
        console.log(combi.join("\n"));
    }

    substrings("dog");

    </script>
</body>
</html>

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Here we arrange and combine a sample string dog, and view the generated results as follows:

Generate all permutations and combinations of strings through JavaScript functions

In the above code, we used several key methods, as follows:

1, pow() method: used to calculate y times of x Power, the syntax is "Math.pow(x,y)".

2, push()Method: You can add one or more elements to the end of the array and return the new length. The syntax is "array.push(item1, item2 , ..., itemX)".

3. join() method: used to put all the elements in the array into a string. The elements are separated by the specified delimiter. The syntax is " arrayObject.join(separator)".

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