题解 | #二分查找-II#利用左端点、右端点注意二分值等于target时要向前寻找，因为可重复

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     * 如果目标值存在返回下标，否则返回 -1
     * @param nums int整型一维数组 
     * @param target int整型 
     * @return int整型
     */
    public int search (int[] nums, int target) {
        if(nums == null || nums.length == 0){
            return -1;
        }
        int left = 0;
        int right = nums.length - 1;
        int middleIndex = 0;
        while(left != right){
            middleIndex = left + (right - left) / 2;
            int middleValue = nums[middleIndex];
            if(target == middleValue){
                while(middleIndex != left && nums[middleIndex -1] == target){
                    middleIndex -= 1;
                }
                return middleIndex;
            } else if(middleValue < target){
                //从右侧找
                left = middleIndex + 1;
            } else {
                //从左侧找
                right = middleIndex - 1;
            }
        }
        if(nums[left] == target){
            return left;
        } else {
            return -1;
        }
    }
}