题解 | #二分查找-II#

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) {
        // write code here
         int f = 0;
        int l = nums.length-1;
        int mid = 0;
        while(f<=l){
            mid = f+(l-f)/2;  //防溢出 等同于（f+l）/2;
            if(target<nums[mid]){
                l = mid-1;
            }
            else if(target>nums[mid]){
                f = mid + 1;
            }
            else {
                while(mid!= 0&&nums[mid] == nums[mid-1]){
                    mid--;
                }
                return mid;
            }

        }
        return -1;
    }
}