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Leetcode 二分查找 Search a 2D Matrix

2024-07-21 08:19:51   219人阅读

Search a 2D Matrix

 Total Accepted: 18506 Total Submissions: 59402My Submissions

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.



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
复杂度：

class Solution {
public:
    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


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