LeetCode 之 Search a 2D Matrix — C 实现

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.

实现高效算法在m×n的整型矩阵中查找指定的值，该矩阵有如下特征：

    每行都是递增的。

    每行的第一个值比上一行最后一个值大。

例如：

考虑下面的矩阵：

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

给定 target  = 3，返回 false。

分析：

采用二分查找。

难点在于对于 mid 求出其在矩阵中对应的行和列。

bool searchMatrix(int** matrix, int matrixRowSize, int matrixColSize, int target) {    int low = 0, high = matrixRowSize * matrixColSize - 1;    int mid = 0, midRow = 0, midCol = 0;        if(!matrix || (matrixRowSize * matrixColSize == 0))/*空指针或空矩阵*/    {        return false;    }        /***二分查找***/    while(low <= high)    {        mid = (low + high)/2;        midRow = mid / matrixColSize; /*属于所在行*/        midCol = mid - midRow * matrixColSize; /*属于所在列*/                if(matrix[midRow][midCol] == target)        {            return true;        }        else if(matrix[midRow][midCol] < target)        {            low = mid + 1;        }        else        {            high = mid - 1;        }    }        return false;}