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// https://inky-hovercraft-849.notion.site/Binary-Search-45031b3e5bce497ca4f0913af31d70c3#4256b911d1ba4eae8e432cd3c439add4

// exact match

import java.util.Arrays;

public final class BasicSolution {

private BasicSolution() {

}

public static int equalTo(final int[] nums, final int target) {

if (nums == null) {

throw new NullPointerException();

}

if (nums.length == 0) {

throw new IllegalArgumentException("The length of nums cannot be zero.");

}

int left = 0, right = nums.length - 1; // left and right always inclusive

while (left <= right) {

final int mid = (right - left) / 2 + left;

if (nums[mid] == target) {

return mid; // return index here

} else if (nums[mid] < target) {

left = mid + 1;

} else {

right = mid - 1;

}

}

throw new IllegalStateException("Cannot find the target value = " + target + " in array = " + Arrays.toString(nums));

}

}

// first occurence

public static int firstOccurrence(final int[] nums, final int target) {

int left = 0, right = nums.length - 1;

while (left < right) {

final int mid = left + (right - left) / 2;

if (nums[mid] >= target) { // condition line

right = mid; // move line

} else {

left = mid + 1; // move line

}

}

// 当我们出来到这里的时候，我们并不知道left指的值是否是满足条件

if (nums[left] >= target) return left; // condition line

return -1;

}

// last occurence

private static int lastOccurrence(final int[] nums, final int target) {

int left = 0, right = nums.length - 1;

while (left < right) {

final int mid = left + (1 + right - left) / 2;

if (nums[mid] <= target) { // condition line

left = mid; // move line

} else {

right = mid - 1; // move line

}

}

// 当我们出来到这里的时候，我们并不知道left指的值是否是满足条件

if (nums[left] <= target) return left; // condition line

return -1;

}