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Copy pathSort012D.java
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60 lines (56 loc) · 1.79 KB
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package com.thealgorithms.misc;
import java.util.*;
/**
* The array is divided into four sections: a[1..Lo-1] zeroes a[Lo..Mid-1] ones
* a[Mid..Hi] unknown a[Hi+1..N] twos If array [mid] =0, then swap array [mid]
* with array [low] and increment both pointers once. If array [mid] = 1, then
* no swapping is required. Increment mid pointer once. If array [mid] = 2, then
* we swap array [mid] with array [high] and decrement the high pointer once.
* For more information on the Dutch national flag algorithm refer
* https://en.wikipedia.org/wiki/Dutch_national_flag_problem
*/
public class Sort012D {
public static void main(String args[]) {
Scanner np = new Scanner(System.in);
int n = np.nextInt();
int a[] = new int[n];
for (int i = 0; i < n; i++) {
a[i] = np.nextInt();
}
sort012(a);
}
public static void sort012(int[] a) {
int l = 0;
int h = a.length - 1;
int mid = 0;
int temp;
while (mid <= h) {
switch (a[mid]) {
case 0:
{
temp = a[l];
a[l] = a[mid];
a[mid] = temp;
l++;
mid++;
break;
}
case 1:
mid++;
break;
case 2:
{
temp = a[mid];
a[mid] = a[h];
a[h] = temp;
h--;
break;
}
}
}
System.out.println("the Sorted array is ");
for (int i = 0; i < a.length; i++) {
System.out.print(+a[i] + " ");
}
}
}