Last Position of Target

ID: 458; easy; 目标最后位置

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Solution 1 (Java)

public class Solution {
    /**
     * @param nums: An integer array sorted in ascending order
     * @param target: An integer
     * @return: An integer
     */
    public int lastPosition(int[] nums, int target) {
        if (nums == null || nums.length == 0)  {
            return -1;
        }

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

        while (left + 1 < right) {
            int mid = left + (right - left) / 2;
            if (nums[mid] <= target) {
                left = mid;
            } else {
                right = mid;
            }
        }

        if (nums[right] == target) return right;
        if (nums[left] == target) return left;
        return -1;
    }
}

Notes

• This is almost the same as finding the first position of target. We return right if possible at the end to ensure that it is the last position of target.