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  • Search a 2D Matrix

    Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:

    • Integers in each row are sorted from left to right.
    • The first integer of each row is greater than the last integer of the previous row.

    For example,

    Consider the following matrix:

    [
      [1,   3,  5,  7],
      [10, 11, 16, 20],
      [23, 30, 34, 50]
    ]
    

    Given target = 3, return true.

    经典的二分查找的题目。

    这题有个特点是每一行有序,且每一行开头数字大于上一行最后的数字,即如果按行flatten,可以拉伸成为一个有序数组。

    思路: 1.先在垂直方向二分,找出行,再在行上二分找出列。复杂度O(logm+logn)2.把数组拉成一维处理(坐标处理为连续的一维),时间复杂度为O(logm*n)==O(logm+logn).

    思路有了,代码简单,就不贴了。

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  • 原文地址:https://www.cnblogs.com/sherylwang/p/5786996.html
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