二分查找

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 left = 0, right = nums.length - 1;
        int idx = -1;
        while (left <= right) {
            int mid = (left + right) >> 1;
            if (nums[mid] == target) {
                idx = mid;
                right = mid - 1;
            } else if (nums[mid] > target) {
                right = mid - 1;
            } else {
                left = mid + 1;
            }
        }
        return idx;
    }
}