leetcode 34 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.

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

跟定一个有序数组和一个目标，如果目标在数组里找到目标的下标，如果不在，找到目标应该插入的位置。

二分查找，找到则返回mid，否则返回r+1或则l。

class Solution {

public:

    int searchInsert(int A[], int n, int target)

    {

        if (n == 0)

            return 0;

        int l = 0, r = n - 1, mid = 0;

        while(l <= r)

        {

            mid = (l + r) / 2;

            if (A[mid] == target)

                return mid;

            if (A[mid] < target)

                l = mid + 1;

            else

                r = mid - 1;

        }

        return l; // 返回的是l，或者是r+1

    }

};

2015/03/31:

从左到右找到相等的或者找到第一次比target大的数的位置即为插入下标位置，但这个是On的，python如下：

class Solution:

    # @param A, a list of integers

    # @param target, an integer to be inserted

    # @return integer

    def searchInsert(self, A, target):

        for i in range(len(A)):

            if A[i] == target or A[i] > target:

                return i

        return len(A)

还是用第一种二分法快吧

巴特西

leetcode 34 Search Insert Position

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