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package Misc;
import java.util.*;
public class RangeInSortedArray {
public static void main(String[] args) {
// Testcases
assert Arrays.equals(sortedRange(new int[] {1, 2, 3, 3, 3, 4, 5}, 3), new int[] {2, 4});
assert Arrays.equals(sortedRange(new int[] {1, 2, 3, 3, 3, 4, 5}, 4), new int[] {5, 5});
assert Arrays.equals(sortedRange(new int[] {0, 1, 2}, 3), new int[] {-1, -1});
}
// Get the 1st and last occurrence index of a number 'key' in a non-decreasing array 'nums'
// Gives [-1, -1] in case element doesn't exist in array
public static int[] sortedRange(int[] nums, int key) {
int[] range = new int[] {-1, -1};
alteredBinSearchIter(nums, key, 0, nums.length - 1, range, true);
alteredBinSearchIter(nums, key, 0, nums.length - 1, range, false);
return range;
}
// Recursive altered binary search which searches for leftmost as well as rightmost occurrence of
// 'key'
public static void alteredBinSearch(
int[] nums, int key, int left, int right, int[] range, boolean goLeft) {
if (left > right) return;
int mid = (left + right) / 2;
if (nums[mid] > key) alteredBinSearch(nums, key, left, mid - 1, range, goLeft);
else if (nums[mid] < key) alteredBinSearch(nums, key, mid + 1, right, range, goLeft);
else {
if (goLeft) {
if (mid == 0 || nums[mid - 1] != key) range[0] = mid;
else alteredBinSearch(nums, key, left, mid - 1, range, goLeft);
} else {
if (mid == nums.length - 1 || nums[mid + 1] != key) range[1] = mid;
else alteredBinSearch(nums, key, mid + 1, right, range, goLeft);
}
}
}
// Iterative altered binary search which searches for leftmost as well as rightmost occurrence of
// 'key'
public static void alteredBinSearchIter(
int[] nums, int key, int left, int right, int[] range, boolean goLeft) {
while (left <= right) {
int mid = (left + right) / 2;
if (nums[mid] > key) right = mid - 1;
else if (nums[mid] < key) left = mid + 1;
else {
if (goLeft) {
if (mid == 0 || nums[mid - 1] != key) {
range[0] = mid;
return;
} else right = mid - 1;
} else {
if (mid == nums.length - 1 || nums[mid + 1] != key) {
range[1] = mid;
return;
} else left = mid + 1;
}
}
}
}
public static int getCountLessThan(int[] nums, int key) {
return getLessThan(nums, key, 0, nums.length - 1);
}
public static int getLessThan(int[] nums, int key, int left, int right) {
int count = 0;
while (left <= right) {
int mid = (left + right) / 2;
if (nums[mid] > key) right = mid - 1;
else if (nums[mid] <= key) {
count = mid + 1; // Atleast mid+1 elements exist which are <= key
left = mid + 1;
}
}
return count;
}
}