LeetCode OJ:Search a 2D Matrix

_王川

于 2014-01-24 23:18:43 发布

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分类专栏： LeetCode 文章标签： leetcode

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本文介绍了一种高效的搜索算法，用于在一特殊性质的二维矩阵中查找指定值。该矩阵的每一行从左到右递增排序，并且每行的第一个元素大于前一行的最后一个元素。文章通过一个具体的例子展示了如何使用二分查找的方法实现这一算法。

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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.

算法思想：二分

class Solution {
public:
    bool searchMatrix(vector<vector<int> > &matrix, int target) {
        if(matrix.empty())return false;
        int r=matrix.size();
        int c=matrix[0].size();
        int left=0,right=r*c-1;
        while(left<=right){
            int mid=(left+right)/2;
            if(matrix[mid/c][mid%c]==target)return true;
            if(matrix[mid/c][mid%c]<target)left=mid+1;
            else right=mid-1;
        }
        return false;
    }
};