L458 Last Position of Target

Find the last position of a target number in a sorted array. Return -1 if target does not exist.

Example

Given[1, 2, 2, 4, 5, 5].

For target =2, return 2.

For target =5, return 5.

For target =6, return -1.

因为这里找last position，所以先判断end是否要找的，再判断start。

public int lastPosition(int[] nums, int target) {
    if (nums == null || nums.length == 0) {
        return -1;
    }

    int start = 0;
    int end = nums.length - 1;

    while (start + 1 < end) {
        int mid = start + (end - start) / 2;

        if (nums[mid] < target) {
            start = mid;
        } else if (nums[mid] > target) {
            end = mid;
        } else {
            start = mid;
        }
    }

    if (nums[end] == target) {
        return end;
    }

    if (nums[start] == target) {
        return start;
    }

    return -1;
}