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RotateArray.java
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179 lines (147 loc) · 3.93 KB
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package codingInterview;
import java.io.IOException;
/**
* for n = 7, k = 3, change [1,2,3,4,5,6,7] to [5,6,7,1,2,3,4]
*
* @author txie
*
*/
public class RotateArray {
public static void main(String[] args) throws IOException {
// TODO Auto-generated method stub
int[] intArray = { 1, 2, 3, 4, 5, 6, 7 };
int length = intArray.length;
int k = 3;
int toK = kTransform(k, length);
/**
while (k < 8) {
int toK = kTransform(k, length);
System.out.print(k + " >>> " + toK + " : ");
rotateArray1(intArray, toK);
k++;
}
**/
// rotateArray2(intArray, k);
// rotateArray3(intArray, toK);
// rotateArray4(intArray, k);
// efficiency test
// for rotateArray1
long startTime = System.nanoTime();
for (int i = 0; i < 100000; i++) {
rotateArray1(intArray, 7);
}
long endTime = System.nanoTime();
System.out
.println(" rotateArray1 cost time : " + (endTime - startTime));
// for rotateArray2
startTime = System.nanoTime();
for (int i = 0; i < 100000; i++) {
rotateArray2(intArray, 7);
}
endTime = System.nanoTime();
System.out
.println(" rotateArray2 cost time : " + (endTime - startTime));
// for rotateArray3
startTime = System.nanoTime();
for (int i = 0; i < 100000; i++) {
rotateArray3(intArray, 7);
}
endTime = System.nanoTime();
System.out
.println(" rotateArray3 cost time : " + (endTime - startTime));
// for rotateArray4
startTime = System.nanoTime();
for (int i = 0; i < 100000; i++) {
rotateArray4(intArray, 7);
}
endTime = System.nanoTime();
System.out
.println(" rotateArray4 cost time : " + (endTime - startTime));
}
private static int kTransform(int k, int length) {
// TODO Auto-generated method stub
if (k > length) {
k = k % length;
} else if (k < 0) {
int n = k / (-length);
k = k + (n + 1) * length;
}
return k;
}
/**
* divide into 2 part, then reverse each part
* like n = 6, k = 2, [1,2,3,4,5,6] --> [1,2,3,4] and [5,6] --> [4,3,2,1] and [6,5]
* --> [4,3,2,1,6,5] --> [5,6,1,2,3,4]
* @param intArray
* @param k
*/
private static void rotateArray4(int[] intArray, int k) {
// TODO Auto-generated method stub
int length = intArray.length;
reverse(intArray, 0, length - k - 1);
reverse(intArray, length - k, length - 1);
reverse(intArray, 0, length - 1);
// for (int i : intArray) {
// System.out.print(i);
// }
}
private static void reverse(int[] intArray, int left, int right) {
int temp;
while (left < right) {
temp = intArray[right];
intArray[right] = intArray[left];
intArray[left] = temp;
left ++;
right --;
}
}
/**
* bubble rotate : like the bubble sort
* O(1) space, but O(k*n) time
* @param intArray
* @param k
*/
private static void rotateArray3(int[] intArray, int k) {
if (intArray == null)
throw new IllegalArgumentException("intArray is null");
int length = intArray.length;
int temp;
for (int i = 0; i < k; i++) {
for(int j = length -1; j > 0; j--) {
temp = intArray[j];
intArray[j] = intArray[j -1];
intArray[j - 1] = temp;
}
}
// for (int i : intArray) {
// System.out.print(i);
// }
}
private static void rotateArray2(int[] intArray, int k) {
// TODO Auto-generated method stub
int length = intArray.length;
int[] result = new int[length];
System.arraycopy(intArray, 0, result, k, length - k);
System.arraycopy(intArray, length - k, result, 0, k);
// for (int i : result) {
// System.out.print(i);
// }
// System.out.println();
}
private static void rotateArray1(int[] intArray, int k) {
// TODO Auto-generated method stub
int length = intArray.length;
int[] result = new int[length];
for (int i = 0; i < length - k; i++) {
result[i + k] = intArray[i];
}
for (int i = 0; i < k; i++) {
result[i] = intArray[length - k + i];
}
// System.arraycopy(result, 0, intArray, 0, length);
// for (int i : result) {
// System.out.print(i);
// }
// System.out.println();
}
}