Closest Number in Sorted Array（lintcode 459)

Description

Given a target number and an integer array A sorted in ascending order, find the index i in A such that A[i] is closest to the given target.

Return -1 if there is no element in the array.

Notice:
There can be duplicate elements in the array, and we can return any of the indices with same value.

Example

Given [1, 2, 3] and target = 2, return 1.

Given [1, 4, 6] and target = 3, return 1.

Given [1, 4, 6] and target = 5, return 1 or 2.

Given [1, 3, 3, 4] and target = 2, return 0 or 1 or 2.

Interface

public class Solution {
    /**
     * @param A an integer array sorted in ascending order
     * @param target an integer
     * @return an integer
     */
    public int closestNumber(int[] A, int target) {
        // Write your code here
    }
}

Solution

public class Solution {
    /**
     * @param A an integer array sorted in ascending order
     * @param target an integer
     * @return an integer
     */
    public int closestNumber(int[] A, int target) {
        // Write your code here
        if (A == null || A.length == 0) {
            return -1;
        }

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

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

            if (A[mid] == target) {
                return mid;
            } else if (A[mid] > target) {
                end = mid;
            } else {
                start = mid;
            }
        }

        return ((target - A[start]) > (A[end] - target)) ? end : start;
    }
}