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Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following properties:
For example,
Consider the following matrix:
[ [1, 3, 5, 7], [10, 11, 16, 20], [23, 30, 34, 50] ]
Given target = 3,
return true.
题意：在一个二维矩阵中找到给定的值。矩阵从上到下从左到右有序
思路：二维空间的二分查找
先在一维里找中间位置，再将该位置转为二维空间里的下标
注：下标比较难弄，得注意点
复杂度： 时间O(log n)，空间O(1)
相关题目：
bool searchMatrix(const vector<vector<int> > &matrix, int target){
if (matrix.empty()) return false;
int m = matrix.size(), n = matrix.front().size();
int begin = 0, end = m * n, middle, row, col;
while(begin < end){
middle = begin + (end - begin) / 2;
int row = middle / n;
int col = middle % n;
if(matrix[row][col] == target) return true;
else if(matrix[row][col] < target) begin = middle + 1;
else end = middle;
}
return false;
}Leetcode 二分查找 Search a 2D Matrix,布布扣,bubuko.com
Leetcode 二分查找 Search a 2D Matrix
原文：http://blog.csdn.net/zhengsenlie/article/details/25746119