JavaScript: Maximum value swapping two digits in an integer

JavaScript Math: Exercise-112 with Solution

Max Value by Digit Swap

Write a JavaScript program to calculate the maximum value by swapping two digits in a given integer.

Test Data:
(100) -> 100
(120) -> 210
(129) -> 921

Sample Solution:

JavaScript Code:

/**
 * Function to find the maximum value by swapping two digits in the given integer.
 * @param {number} n - The integer.
 * @returns {number} - The maximum value obtained after swapping two digits, if any.
 */
function test(n) {
    // Convert the integer to a string
    var n_str = n.toString();
    
    // Loop through each digit of the integer
    for (var i = 0; i < n_str.length; i++) {
        var t = n_str[i]; // Current digit
        var index = i; // Index of the current digit
            
        // Find the maximum digit greater than the current digit
        for (var x = n_str.length - 1; x > i; x--) {
            if (n_str[x] > t) {
                t = n_str[x];
                index = x;
            }
        }
        
        // If a greater digit is found, swap the digits and return the new integer
        if (t != n_str[i]) {
            var nums = n_str.split('');
            
            var tmp = nums[i];
            
            nums[i] = nums[index];
            nums[index] = tmp;
            
            return parseInt(nums.join(''));
        }
    }
    // If no swap is possible, return the original integer
    return n;
}

// Test cases
n = 100;
console.log("n = " + n);
console.log("Maximum value swapping two digits in the said integer: " + test(n));
n = 120;
console.log("n = " + n);
console.log("Maximum value swapping two digits in the said integer: " + test(n));
n = 129;
console.log("Maximum value swapping two digits in the said integer: " + test(n));
console.log("e: " + test(n));

Output:

n = 100
Maximum value swapping two digits in the said integer: 100
n = 120
Maximum value swapping two digits in the said integer: 210
Maximum value swapping two digits in the said integer: 921
e: 921

Flowchart:

Live Demo:

See the Pen javascript-math-exercise-112 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript function that finds the maximum possible value by swapping two digits in a given number.
• Write a JavaScript function that converts a number to a string, explores all single-swap possibilities, and returns the maximum value.
• Write a JavaScript function that iterates over digit pairs to determine the best swap that results in the highest number.
• Write a JavaScript function that handles edge cases such as numbers with identical digits and returns the original number if no beneficial swap exists.

Improve this sample solution and post your code through Disqus.

Previous: Kth smallest number in a multiplication table.
Next: Smallest number whose digits multiply to a number.