704.二分查找
这题之前做过，但这次做的时候边界忘了加减错了一次。
求中值防溢出可以换成:int middle = left + ((right - left) / 2);

 public int search(int[] nums, int target) {
        return binarySearch(nums,target,0,nums.length-1);
    }
    public int binarySearch(int[] nums, int target,int start,int end) {
        int mid = (start+end) / 2;
        if (nums[mid] == target){
            return mid;
        }else{
            if(start >= end) return -1;
            if (nums[mid] < target){
                return binarySearch(nums,target,mid+1,end);
            }else {
                return binarySearch(nums,target,start,mid-1);
            }
        }
    }

27.移除元素
这题没什么好说的，快慢指针。

    public int removeElement(int[] nums, int val) {
        int left = 0;
        int right = 0;
        while (left < nums.length){
            if (nums[left] != val){
                nums[right] = nums[left];
                right++;
            }
            left++;
        }
        return right;
    }