方法一：从小到大暴力搜索

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

方法二：二分查找

二分查找有一些边界值容易出错，写完代码手动验证一下：
1、nums为空串
2、nums所有元素都比target小
3、nums所有元素都比target大

class Solution {
    public int searchInsert(int[] nums, int target) {
        if(nums.length==0)return 0;//空串
        int left = 0;
        int right = nums.length-1;
        int mid = 0;
        while(left<right){
            mid = (left+right)/2;
            if(nums[mid]==target)return mid;
            else if(nums[mid]>target)right = mid-1;
            else left = mid+1;
        }
        if(right<0)return 0;
        if(nums[right]<target)return right+1;
        else return right;
    }
}