题解 | #找出特定体重的牛群#

考察二分查找。需要对于边界进行把握，寻找左边界时如果中间值更大就向右移动，反之就将其更新到中间处。寻找右边界时候，如果中间值小于target，就将右边界向左移动到mid-1，反之将左边界移动到mid

完整Java代码如下

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
     *
     *
     * @param weights int整型一维数组
     * @param target int整型
     * @return int整型一维数组
     */
    public int[] searchRange (int[] weights, int target) {
        // write code here
        int start = 0;
        int end = weights.length - 1;
        while (start <= end) {
            int mid = (start + end) / 2;
            if (weights[mid] < target) {
                end = mid - 1;
            } else if (weights[mid] > target) {
                start = mid + 1;
            } else {
                start = mid;
                end = mid;
                while (start >= 0 && weights[start] == target) {
                    start--;
                }
                while (end < weights.length && weights[end] == target) {
                    end++;
                }
                return new int[] {start + 1, end - 1};
            }
        }
        return new int[] {-1, -1};
    }
}