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96 lines (75 loc) · 2.52 KB
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package RecursionArray;
import java.lang.reflect.Array;
import java.util.ArrayList;
public class Findelements {
public static void main(String[] args) {
// int[] arr = {2, 3, 1, 4, 4, 5};
// System.out.println(find(arr, 4, 0));
// System.out.println(findIndex(arr, 4, 0));
// System.out.println(findIndexLast(arr, 4, arr.length - 1));
// findAllIndex(arr, 4, 0);
// System.out.println(list);
//
// ArrayList<Integer> ans = findAllIndex(arr, 4, 0, new ArrayList<>());
// System.out.println(ans);
System.out.println(findAllIndex2(new int[]{2, 3, 1, 4, 4, 5}, 4, 0));
}
static boolean find(int[] arr, int target, int index) {
if (index == arr.length) {
return false;
}
return arr[index] == target || find(arr, target, index + 1);
}
static int findIndex(int[] arr, int target, int index) {
if (index == arr.length) {
return -1;
}
if (arr[index] == target) {
return index;
} else {
return findIndex(arr, target, index + 1);
}
}
static int findIndexLast(int[] arr, int target, int index) {
if (index == -1) {
return -1;
}
if (arr[index] == target) {
return index;
} else {
return findIndexLast(arr, target, index - 1);
}
}
static ArrayList<Integer> list = new ArrayList<>();
static void findAllIndex(int[] arr, int target, int index) {
if (index == arr.length) {
return;
}
if (arr[index] == target) {
list.add(index);
}
findAllIndex(arr, target, index + 1);
}
static ArrayList<Integer> findAllIndex(int[] arr, int target, int index, ArrayList<Integer> list) {
if (index == arr.length) {
return list;
}
if (arr[index] == target) {
list.add(index);
}
return findAllIndex(arr, target, index + 1, list);
}
static ArrayList<Integer> findAllIndex2(int[] arr, int target, int index) {
ArrayList<Integer> list = new ArrayList<>();
if (index == arr.length) {
return list;
}
//this will contain answer for that function call only and not for the whole recursion
if (arr[index] == target) {
list.add(index);
}
ArrayList<Integer> ansFromBelowCalls = findAllIndex(arr, target, index + 1, list);
list.addAll(ansFromBelowCalls);
return list;
}
}