54 lines
1.7 KiB
Java
54 lines
1.7 KiB
Java
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package Misc;
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import java.util.*;
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/**
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The array is divided into four sections:
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a[1..Lo-1] zeroes
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a[Lo..Mid-1] ones
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a[Mid..Hi] unknown
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a[Hi+1..N] twos
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If array [mid] =0, then swap array [mid] with array [low] and increment both pointers once.
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If array [mid] = 1, then no swapping is required. Increment mid pointer once.
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If array [mid] = 2, then we swap array [mid] with array [high] and decrement the high pointer once.
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For more information on the Dutch national flag algorithm refer https://en.wikipedia.org/wiki/Dutch_national_flag_problem
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*/
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public class Sort012D {
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public static void main(String args[]) {
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Scanner np = new Scanner(System.in);
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int n = np.nextInt();
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int a[] = new int[n];
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for (int i = 0; i < n; i++) {
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a[i] = np.nextInt();
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}
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sort012(a);}
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public static void sort012(int[]a){
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int l = 0;
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int h = a.length - 1;
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int mid = 0;
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int temp ;
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while (mid <= h) {
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switch (a[mid]) {
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case 0: {
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temp = a[l];
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a[l] = a[mid];
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a[mid] = temp;
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l++;
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mid++;
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break;}
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case 1:
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mid++;
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break;
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case 2: {
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temp = a[mid];
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a[mid] = a[h];
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a[h] = temp;
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h--;
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break;
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}
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}
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}
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System.out.println("the Sorted array is ");
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for (int i = 0; i < a.length; i++)
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System.out.print(+a[i] + " "); }
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}
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