Search for a range (find start and end indices of target in sorted array)?

public int[] SearchRange(int[] nums, int target) {
int left = FindBoundary(nums, target, true);
int right = FindBoundary(nums, target, false);
return new int[] { left, right };
}
private int FindBoundary(int[] nums, int target, bool findFirst) {

Follow on:

int left = 0, right = nums.Length - 1;
int boundary = -1;

while (left <= right) {

int mid = left + (right - left) / 2;
if (nums[mid] == target) {
boundary = mid;
if (findFirst)
right = mid - 1;

else

left = mid + 1;
}
else if (nums[mid] < target) left = mid + 1;
else right = mid - 1;
}
return boundary;
}

Explanation:

Binary search twice — once to find first occurrence and once for last occurrence.