mirror of https://github.com/evanferrao/dsa
87 lines
2.3 KiB
Java
87 lines
2.3 KiB
Java
// write a code of mergesort using function in java
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import java.util.Scanner;
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public class MergeSort{
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// use notation beginning, mid and end
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public static void main(String[] args){
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Scanner sc = new Scanner(System.in);
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System.out.println("Enter the size of the array: ");
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int n = sc.nextInt();
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int[] arr = new int[n];
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System.out.println("Enter the elements of the array: ");
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for(int i=0; i<n; i++){
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arr[i] = sc.nextInt();
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}
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mergeSort(arr, 0, n-1);
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System.out.println("The sorted array is: ");
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for(int i=0; i<n; i++){
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System.out.print(arr[i] + " ");
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}
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sc.close();
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}
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static void mergeSort(int arr[], int beginning, int end){
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if(beginning < end){
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// find the middle point
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int mid = (beginning + end) / 2;
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// sort first and second halves
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mergeSort(arr, beginning, mid);
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mergeSort(arr, mid + 1, end);
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// merge the sorted halves
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merge(arr, beginning, mid, end);
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}
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}
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static void merge(int arr[], int beginning, int mid, int end){
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// find the size of two subarrays to be merged
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int n1 = mid - beginning + 1;
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int n2 = end - mid;
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// create temp arrays
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int L[] = new int[n1];
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int R[] = new int[n2];
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// copy data to temp arrays
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for(int i = 0; i < n1; i++){
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L[i] = arr[beginning + i];
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}
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for(int j = 0; j < n2; j++){
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R[j] = arr[mid + 1 + j];
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}
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// merge the temp arrays
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// initial indexes of first and second subarrays
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int i = 0, j = 0;
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// initial index of merged subarray array
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int k = beginning;
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while(i < n1 && j < n2){
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if(L[i] <= R[j]){
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arr[k] = L[i];
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i++;
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}else{
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arr[k] = R[j];
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j++;
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}
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k++;
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}
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// copy remaining elements of L[] if any
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while(i < n1){
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arr[k] = L[i];
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i++;
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k++;
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}
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// copy remaining elements of R[] if any
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while(j < n2){
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arr[k] = R[j];
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j++;
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k++;
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}
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}
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}
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