二分

import java.util.*;

public class Solution {
    public int search (int[] nums, int target) {
        int n = nums.length;
        int l = 0,r = n - 1;
        while(l < r){
            int mid = l + r >> 1;
            if(nums[mid] >= target)r = mid;
            else l = mid + 1;
        }
        if(n == 0 || nums[l] != target)l = -1;
        return l;
    }
}