扫描一遍

class Solution {
    public int search(int[] nums, int target) {
        int ans = 0;
        for(int i = 0; i < nums.length; i ++){
            if(nums[i] == target) ans ++;
        }

        return ans;
    }
}

二分
第一次出现和最后一次出现的位置

class Solution {
    public int search(int[] nums, int target) {
        if(nums.length == 0) return 0;

        int l = 0;
        int r = nums.length - 1;
        //找到第一个点
        while(l < r){
            int mid = l + r >> 1;
            if(nums[mid] < target) l = mid + 1;
            else r = mid;
        }

        if(nums[l] != target) return 0;
        int left = l;

        l = 0;
        r = nums.length - 1;
        while(l < r){
            int mid = l + r + 1 >> 1;
            if(nums[mid] <= target) l = mid;
            else r = mid - 1;
        }

        return r - left + 1;

    }
}