[2019.01.09] Sorting

Problem

Objective 
Today, we're discussing a simple sorting algorithm called Bubble Sort. Check out the Tutorial tab for learning materials and an instructional video!

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Consider the following version of Bubble Sort:

for (int i = 0; i < n; i++) {
    // Track number of elements swapped during a single array traversal
    int numberOfSwaps = 0;
    
    for (int j = 0; j < n - 1; j++) {
        // Swap adjacent elements if they are in decreasing order
        if (a[j] > a[j + 1]) {
            swap(a[j], a[j + 1]);
            numberOfSwaps++;
        }
    }
    
    // If no elements were swapped during a traversal, array is sorted
    if (numberOfSwaps == 0) {
        break;
    }
}

Task 
Given an array, , of size  distinct elements, sort the array in ascending order using the Bubble Sort algorithm above. Once sorted, print the following  lines:

1. Array is sorted in numSwaps swaps. 
   where  is the number of swaps that took place.
2. First Element: firstElement 
   where  is the first element in the sorted array.
3. Last Element: lastElement 
   where  is the last element in the sorted array.

Hint: To complete this challenge, you will need to add a variable that keeps a running tally of all swaps that occur during execution.

Input Format

The first line contains an integer, , denoting the number of elements in array . 
The second line contains  space-separated integers describing the respective values of .

Constraints

• , where .

Output Format

Print the following three lines of output:

1. Array is sorted in numSwaps swaps. 
   where  is the number of swaps that took place.
2. First Element: firstElement 
   where  is the first element in the sorted array.
3. Last Element: lastElement 
   where  is the last element in the sorted array.

Sample Input 0

3
1 2 3

Sample Output 0

Array is sorted in 0 swaps.
First Element: 1
Last Element: 3

Explanation 0

The array is already sorted, so  swaps take place and we print the necessary  lines of output shown above.

Sample Input 1

3
3 2 1

Sample Output 1

Array is sorted in 3 swaps.
First Element: 1
Last Element: 3

Explanation 1

The array  is not sorted, so we perform the following  swaps:

At this point the array is sorted and we print the necessary  lines of output shown above.

How I solved the problem

# key word : Bubble Sort(버블정렬)

  - 앞의 요소와 그 다음 요소를 비교하여 그 다음 요소보다 앞의 요소가 더 클 경우 swap이 일어남.

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;
 
public class Solution {
 
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        int[] a = new int[n];
        for(int a_i=0; a_i < n; a_i++){
            a[a_i] = in.nextInt();
        }
        // Write Your Code Here
 
        int swapCount = 0; // swap 횟수
 
        for (int i = 0; i < n; i++) {
            for (int j = 0; j < n - (i + 1); j++) {
                if (a[j] > a[j + 1]) {
                    int temp = a[j];
                    a[j] = a[j + 1];
                    a[j + 1] = temp;
                    swapCount++;
                }
            }
        }
 
        System.out.println("Array is sorted in " + swapCount + " swaps.");
        System.out.println("First Element: " + a[0]);
        System.out.println("Last Element: " + a[n-1]);
    }
}
 
 

[출처 : https://www.hackerrank.com ]