Question

java 怎么交换同一数组里面的两部分元素的位置 像 ｛1,2,3,4,5,6｝ 最后结果是｛4

java 怎么交换同一数组里面的两部分元素的位置
像 ｛1,2,3,4,5,6｝
最后结果是｛4,5,6,1,2,3｝把前半部分和后半部分交换

Answer 1

public class TDemo {
	public static void main(String[] args) {
		int []arr= {1,2,3,4,5,6};
		exchange(arr,3);
		
		for (int i = 0; i < arr.length; i++) {
			System.out.println(arr[i]);
		}
	}

	/**
	 * @param arr 需要交换的数组
	 * @param index 交换的位置
	 */
	private static void exchange(int[] arr,int index) {
		int []temp=new int[arr.length];
		int t=0;
		for (int i = index; i < arr.length; i++) {
			temp[t++]=arr[i];
		}
		for (int i = 0; i < arr.length-index; i++) {
			temp[t++]=arr[i];
		}
		for (int i = 0; i < temp.length; i++) {
			arr[i]=temp[i];
		}
	}
}

Answer 2

假设你的数组元素个数是偶数。。

i指向最开始的1，j指向中间元素（比如4），然后交换a[i]和a[j]，然后i++和j++，再继续交换a[i]和a[j]，一直重复到 j 达到最后。

void swap(int[] a) {
  int i = 0, j = a.length / 2;
  for(; j<a.length; i++, j++) {
    int tmp = a[i];
    a[j] = tmp;
    a[i] = a[j];
  }
}

Answer 3

import java.util.Arrays;

public class BaiduZhidao {

/**
* @param args the command line arguments
*/
public int[] randomCommon(int min, int max, int n) {
if (n > (max - min + 1) || max < min) {
return null;
}
int[] result = new int[n];
int count = 0;
while (count < n) {
int num = (int) (<a href="https://www.baidu.com/s?wd=Math.random&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1dBP1N-njDsnAnsuHDvm1Ts0AP8IA3qPjfsn1bkrjKxmLKz0ZNzUjdCIZwsrBtEXh9GuA7EQhF9pywdQhPEUiqkIyN1IA-EUBtkrj61nHT4PWnLnHfkPHb3nH03" target="_blank" class="baidu-highlight">Math.random</a>() * (max - min)) + min;
boolean flag = true;
for (int j = 0; j < n; j++) {
if (num == result[j]) {
flag = false;
break;
}
}
if (flag) {
result[count] = num;
count++;
}
}
return result;
}

public static void main(String[] args) {
int a[] = {1, 2, 3, 4, 5, 6};
int index[] = new int[3];
index = new BaiduZhidao().randomCommon(0, 7, 3);

int r1[] = new int[6];
int r2[] = new int[6];
int r3[] = new int[6];
int r4[] = new int[6];

for (int i = 0; i < index.length; i++) {
index[i] = index[i] - 1;
}

<a href="https://www.baidu.com/s?wd=Arrays.sort&tn=44039180_cpr&fenlei=mv6quAkxTZn0IZRqIHckPjm4nH00T1dBP1N-njDsnAnsuHDvm1Ts0AP8IA3qPjfsn1bkrjKxmLKz0ZNzUjdCIZwsrBtEXh9GuA7EQhF9pywdQhPEUiqkIyN1IA-EUBtkrj61nHT4PWnLnHfkPHb3nH03"target="_blank" class="baidu-highlight">Arrays.sort</a>(index);

r1 = Arrays.copyOf(a, a.length);
r2 = Arrays.copyOf(a, a.length);
r3 = Arrays.copyOf(a, a.length);
r4 = Arrays.copyOf(a, a.length);
r1[index[0]] = a[index[1]];
r1[index[1]] = a[index[0]];
r1[index[2]] = a[index[2]];

r2[index[0]] = a[index[1]];
r2[index[1]] = a[index[2]];
r2[index[2]] = a[index[0]];

r3[index[0]] = a[index[2]];
r3[index[1]] = a[index[0]];
r3[index[2]] = a[index[1]];

r4[index[0]] = a[index[2]];
r4[index[1]] = a[index[1]];
r4[index[2]] = a[index[0]];

for (int i = 0; i < r1.length; i++) {
System.out.print(r1[i] + " ");
}
System.out.println();
for (int i = 0; i < r1.length; i++) {
System.out.print(r2[i] + " ");
}
System.out.println();
for (int i = 0; i < r1.length; i++) {
System.out.print(r3[i] + " ");
}
System.out.println();
for (int i = 0; i < r1.length; i++) {
System.out.print(r4[i] + " ");
}

}

}

Answer 4

public class Foo {

	public static void main(String[] args) {
		int[] n={1,2,3,4,5,6};
		print(n);
		change(n);
		System.out.println();
		print(n);
	}

	public static void change(int[] n) {
		if (n == null || n.length < 2)
			return;
		int index = n.length / 2 + n.length % 2;
		for (int i = 0; i < n.length / 2; i++, index++) {
			int temp = n[i];
			n[i] = n[index];
			n[index] = temp;
		}
	}
	public static void print(int[] n){
		for(int i=0;i<n.length;i++){
			System.out.print(n[i]+" ");
		}
	}
}