'Reversing an array using a stack
I am attempting to reverse an array using a stack. However, I get an error on arr[i] = stack.top();
, and the suggestion to resolve it in Eclipse is to change it to arr[i] = stack.pop();
or to add a cast. Is there another way about this or have I made a mistake?
I see tutorials and questions asking about how to reverse a string using a stack and I have tried to reverse an array using the same logic, but I'm not entirely sure where I'm going wrong.
public static void reverse(String[] arr){
Stack stack = new Stack();
for(int i = 0; i < arr.length; i++) {
stack.push(arr[i]);
}
for(int i = 0; i < arr.length; i++) {
arr[i] = stack.top();
stack.pop();
}
return;
}
Solution 1:[1]
When you pop the stack, it returns the object at the top and removes it from the stack. Try this:
public static void reverse(String[] arr){
Stack stack = new Stack();
for(int i = 0; i < arr.length; i++) {
stack.push(arr[i]);
}
for(int i = 0; i <arr.length;i++) {
arr[i] = stack.pop();
}
}
Solution 2:[2]
Method top
doesn't exist in the Stack
of Java. The similar method you're looking for is peek
. Take a look at http://docs.oracle.com/javase/7/docs/api/java/util/Stack.html
However, you can use only pop
, because it returns the removed object.
Solution 3:[3]
Reverse int array using stack
static int[] reverseArray(int[] arr) {
Stack < String > stack = new Stack();
int len = arr.length;
String[] strArr = new String[len];
for (int i = 0; i < arr.length; i++) {
strArr[i] = String.valueOf(arr[i]);
stack.push(strArr[i]);
}
for (int i = 0; i < strArr.length; i++) {
strArr[i] = stack.pop();
arr[i] = Integer.parseInt(strArr[i]);
}
return arr;
}
Solution 4:[4]
import java.util.Arrays;
import java.util.Stack;
public class reverse {
public static void main(String[]args){
Integer arr[] = {3,5,6,8};
Stack<Integer> st = new Stack<>();
for(int i =0;i<arr.length;i++){
st.push(arr[i]);
}
for(int i =0;i<arr.length;i++){
arr[i]=st.peek();
st.pop();
}
System.out.println(Arrays.toString(arr));
}
}
Sources
This article follows the attribution requirements of Stack Overflow and is licensed under CC BY-SA 3.0.
Source: Stack Overflow
Solution | Source |
---|---|
Solution 1 | Stack Underflow |
Solution 2 | Hugo Sousa |
Solution 3 | |
Solution 4 | Pranshu vashisth |