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62 lines (49 loc) · 1.72 KB
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package sort;
import org.junit.Test;
import utils.Utils;
import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;
public class QuickSort {
/*
TASK
Quick sort를 구현한다.
*/
@Test
public void test() {
int[] arr1 = {};
int[] sortedArr1 = {};
assertThat(solution(arr1, 0, arr1.length - 1), is(sortedArr1));
int[] arr2 = {6,4,1,8,9,2,7,5,3};
int[] sortedArr2 = {1,2,3,4,5,6,7,8,9};
assertThat(solution(arr2, 0, arr2.length - 1), is(sortedArr2));
int[] arr4 = {6,4,2,10,9,1,7,11,5,3,0,8};
int[] sortedArr4 = {0,1,2,3,4,5,6,7,8,9,10,11};
assertThat(solution(arr4, 0, arr4.length - 1), is(sortedArr4));
int[] arr3 = {1};
int[] sortedArr3 = {1};
assertThat(solution(arr3, 0, arr3.length - 1), is(sortedArr3));
}
public int[] solution(int[] arr, int left, int right) {
if (arr == null) return null;
int[] result = arr;
if (left >= right) return result;
int pivotPos = partition(result, left, right);
result = solution(result, left, pivotPos - 1);
result = solution(result, pivotPos + 1, right);
return result;
}
private int partition(int[] arr, int left, int right) {
if (arr == null || left < 0) return -1;
int pivotValue = arr[right];
int endOfLowBlock = left - 1;
for (int pos = left; pos < right; ++pos) {
if (pivotValue > arr[pos]) {
endOfLowBlock += 1;
Utils.swapValue(arr, pos, endOfLowBlock);
}
}
endOfLowBlock += 1;
Utils.swapValue(arr, right, endOfLowBlock);
return endOfLowBlock;
}
}