我试图在Java中反转一个int数组。
此方法不反转数组。
for(int i = 0; i < validData.length; i++)
{
int temp = validData[i];
validData[i] = validData[validData.length - i - 1];
validData[validData.length - i - 1] = temp;
}
有什么问题吗?
我试图在Java中反转一个int数组。
此方法不反转数组。
for(int i = 0; i < validData.length; i++)
{
int temp = validData[i];
validData[i] = validData[validData.length - i - 1];
validData[validData.length - i - 1] = temp;
}
有什么问题吗?
当前回答
另一种反向数组的方法
public static int []reversing(int[] array){
int arraysize = array.length;
int[] reverse = new int [arraysize+1];
for(int i=1; i <= arraysize ; i++){
int dec= arraysize -i;
reverse[i] = array[dec];
}
return reverse;
}
其他回答
以下是我想到的:
// solution 1 - boiler plated
Integer[] original = {100, 200, 300, 400};
Integer[] reverse = new Integer[original.length];
int lastIdx = original.length -1;
int startIdx = 0;
for (int endIdx = lastIdx; endIdx >= 0; endIdx--, startIdx++)
reverse[startIdx] = original[endIdx];
System.out.printf("reverse form: %s", Arrays.toString(reverse));
// solution 2 - abstracted
// convert to list then use Collections static reverse()
List<Integer> l = Arrays.asList(original);
Collections.reverse(l);
System.out.printf("reverse form: %s", l);
这里有一个简单快速的解决方案。希望能有所帮助!
public int[] reverse(int[] arr) {
for(int i = arr.length; i > 0 ; i--){
System.out.print(arr[i-1] + " ");
}
return arr;
}
在Java 8的情况下,我们还可以使用IntStream来反转整数数组:
int[] sample = new int[]{1,2,3,4,5};
int size = sample.length;
int[] reverseSample = IntStream.range(0,size).map(i -> sample[size-i-1])
.toArray(); //Output: [5, 4, 3, 2, 1]
public void display(){
String x[]=new String [5];
for(int i = 4 ; i > = 0 ; i-- ){//runs backwards
//i is the nums running backwards therefore its printing from
//highest element to the lowest(ie the back of the array to the front) as i decrements
System.out.println(x[i]);
}
}
我认为如果你声明显式变量来跟踪你在每次循环迭代中交换的下标,那么遵循算法的逻辑会更容易一些。
public static void reverse(int[] data) {
for (int left = 0, right = data.length - 1; left < right; left++, right--) {
// swap the values at the left and right indices
int temp = data[left];
data[left] = data[right];
data[right] = temp;
}
}
我还认为在while循环中执行这个操作更具可读性。
public static void reverse(int[] data) {
int left = 0;
int right = data.length - 1;
while( left < right ) {
// swap the values at the left and right indices
int temp = data[left];
data[left] = data[right];
data[right] = temp;
// move the left and right index pointers in toward the center
left++;
right--;
}
}