Given a target number and an integer array A sorted in ascending order, find the indexiin 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, return1.

Given[1, 4, 6]and target =3, return1.

Given[1, 4, 6]and target =5, return1or2.

Given[1, 3, 3, 4]and target =2, return0or1or2.

分析

典型二分法模板， 主要关注在出了循环后，对target， begin ，end三个值大小判断的三种情况

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

        while(begin + 1 < end){
            int mid = begin + (end - begin)/2;
            if(A[mid] == target){
                return mid;
            }else if(A[mid] > target){
                end = mid;
            }else{
                begin = mid;
            }
        }

        if(A[begin] >= target){
            return begin;
        }else if (A[end] <=  target){
            return end;
        }

        if(target - A[begin] < A[end] - target){
            return begin;
        }else{
            return end;
        }


    }
}