LeetCode | 35. Search Insert Position

原创于 2017-06-05 20:17:24 发布 · 275 阅读

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本文介绍了一种在已排序数组中查找目标值的二分查找算法，并提供了完整的C++实现代码。该算法不仅能找到目标值的位置，还能确定目标值若不存在时应插入的位置。

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.

Here are few examples.
[1,3,5,6], 5 → 2
[1,3,5,6], 2 → 1
[1,3,5,6], 7 → 4
[1,3,5,6], 0 → 0

简单的二分查找，直接贴上代码：

class Solution {
public:
    int searchInsert(vector<int>& nums, int target)
    {
        int len = nums.size();
        int left = 0, right = len-1;

        if(nums[len-1] < target)    //插在末位
            return len;
        if(nums[0] > target)    //插在首位
            return 0;

        while(left <= right)
        {
            int mid = (left+right)/2;
            if(nums[mid] == target)
                return mid;
            if(nums[mid] < target)
            {
                if(nums[mid+1] > target)
                    return mid+1;
                else
                {
                    left = mid+1;
                }
            }
            else
                right = mid-1;
        }

        return -1;
    }
};