Hello! Today we will learn how to solve coding test problems with JavaScript. The topic of this tutorial is ‘Finding the K-th Number’. Through this problem, we will learn how to sort an array and find the value at a specific index. Let’s look at the problem statement and the solution process step by step.<\/p>\n
You need to find the K-th number that satisfies certain conditions from the given array. The specific problem description is as follows.<\/p>\n
\nProblem: Finding the K-th Number\n\nGiven an array and an integer K, you need to return the K-th smallest number after sorting the array in ascending order.\n\nInput:\n- First line: Integer N (length of the array), Integer K (position of the number to find)\n- Second line: An array of N integers\n\nOutput:\n- K-th smallest number\n<\/pre>\nExample<\/h3>\n
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- Input:
5 2<\/code><\/li>\n- Array:
[3, 1, 2, 5, 4]<\/code><\/li>\n- Output:
2<\/code><\/li>\n<\/ul>\nFrom the above input values, if we sort the array in ascending order, it becomes
[1, 2, 3, 4, 5]<\/code>, and the 2nd number is2<\/code>.<\/p>\nSolution Process<\/h2>\n
The steps required to solve the problem are as follows.<\/p>\n
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- Read the input values and set the array and K.<\/li>\n
- Sort the array in ascending order.<\/li>\n
- Output the value at the K-th index.<\/li>\n<\/ol>\n
Step 1: Read Input Values<\/h3>\n
In JavaScript, you can use the
prompt<\/code> function to receive input values. However, coding test platforms usually read values through standard input. Here, we will directly declare the array for testing.<\/p>\n\nconst arr = [3, 1, 2, 5, 4];\nconst K = 2; \/\/ K-th number\n<\/code><\/pre>\nStep 2: Sort the Array<\/h3>\n
In JavaScript, you can use the
sort<\/code> method to sort an array. This method performs string sorting by default, so you need to provide a callback function for number sorting.<\/p>\n\narr.sort((a, b) => a - b);\n<\/code><\/pre>\nThe above code sorts the array in ascending order, meaning it arranges from the smallest number to the largest number.<\/p>\n
Step 3: Return the K-th Number<\/h3>\n
Since array indices start at 0, to get the K-th number, you need to use
K-1<\/code> as the index. Therefore, you can do the following.<\/p>\n\nconst kthNumber = arr[K - 1];\nconsole.log(kthNumber); \/\/ Output\n<\/code><\/pre>\nComplete Code<\/h2>\n
Now, let’s combine all the steps and write the complete code.<\/p>\n
\nfunction findKthNumber(arr, K) {\n \/\/ Sort the array in ascending order\n arr.sort((a, b) => a - b);\n \n \/\/ Return the K-th number (K is 1-based index, so use K-1)\n return arr[K - 1];\n}\n\n\/\/ Test\nconst arr = [3, 1, 2, 5, 4]; \/\/ Example array\nconst K = 2; \/\/ K-th number\nconst result = findKthNumber(arr, K);\nconsole.log(result); \/\/ Output result: 2\n<\/code><\/pre>\nConclusion<\/h2>\n