I want to find the last occurrence of x(13) in the array which is 6, but my code only finds the first occurrences which is 4, is there a way I can solve this?
/* Application Program */
int[] arr = {9, 12, 2, 8, 13, -8, 13, 9};
int index = lastIndexOf(arr, 13);
if(index != -1)
System.out.println(index);
else
System.out.println("not found");
/* Method */
public static int lastIndexOf(int[] arr, int x){
for(int i = 0; i<arr.length; i++){
if(arr[i] == x){
return i;
}
}
return -1;
}
Iterate the array backwards. Like,
public static int lastIndexOf(int[] arr, int x) {
for (int i = arr.length - 1; i >= 0; i--) {
if (arr[i] == x) {
return i;
}
}
return -1;
}
If you are scanning from the first element to the last element, you should store the result in a variable.
public static int lastIndexOf(int[] arr, int x)
{
int resultIndex = -1;
for(int i = 0; i < arr.length; i++)
if(arr[i] == x)
resultIndex = i;
return resultIndex;
}
If you're scanning from the last element to the first element, you can return the result directly from the method.
public static int lastIndexOf(int[] arr, int x)
{
for(int i = arr.length - 1 ; i >= 0; --i)
if(arr[i] == x)
return i;
return -1;
}
you want to find the last occurrence of 13 but you are returning the index in very first match itself.
public static int lastIndexOf(int[] arr, int x){
for(int i = 0; i<arr.length; i++){
if(arr[i] == x){
return i;
}
}
return -1;
}
In order to return the last occurrence you can modify the code and return the most recent index.
public static int lastIndexOf(int[] arr, int x){
int lastIndex = -1
for(int i = 0; i<arr.length; i++){
if(arr[i] == x){
lastIndex = i;
}
}
return lastIndex;
}
Using java Map based approach.
public static int lastIndexOfV1(int[] arr, int x) {
Map<Integer, Integer> map = new HashMap<>();
for (int i = 0; i < arr.length; i++) {
map.put(arr[i], i);
}
return map.get(x);
}