LeetCode-35.Search Insert Position

Given a sorted array and a target value, return the index if the target is found. If not, return the index where it would be if it were inserted in order.

You may assume no duplicates in the array.

Example 1:

Input: [1,3,5,6], 5
Output: 2

Example 2:

Input: [1,3,5,6], 2
Output: 1

Example 3:

Input: [1,3,5,6], 7
Output: 4

Example 4:

Input: [1,3,5,6], 0
Output: 0

二分查找，查找第一个大于等于给定值的元素，即插入位置，时间复杂度O（logn）

    public int searchInsert(int[] nums, int target) {
        if(null == nums || 0== nums.length){
            return -1;
        }
        int left =0;
        int right =nums.length-1;
        while(left<=right){
            int mid = left+((right-left)>>1);
            if(nums[mid]<target){
                left = mid+1;
            }
            else if(mid ==0|| nums[mid-1]<target){//若干是第一个大于等于target的值
                return mid;
            }
            else{
                right = mid-1;
            }
        }
        return nums.length;
    }