leetcode_74题——Search a 2D Matrix（数组查找）

Search a 2D Matrix

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Question Solution

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.

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Array Binary Search

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#include<iostream>
#include <vector>
using namespace std;

/*这道题是在一个排好序的数组中查找一个指定的数
  从上到下递增，从左到右递增，所以从右往左，每次与最上面的那个数作比较*/
bool searchMatrix(vector<vector<int>>& matrix, int target) {
	int x=matrix.size();
	int y=matrix[0].size();

	for(int j=y-1;j>=0;j--)
	{
		if(target==matrix[0][j])
			return true;
		if(target>matrix[0][j])
		{
			for(int i=1;i<=x-1;i++)
				if(target==matrix[i][j])
					return true;
		}
	}
	return false;
}

int main()
{
	vector<vector<int> > vec0;
	vector<int> vec;
	vec.push_back(1);
	vec0.push_back(vec);
	vec.clear();
	vec.push_back(3);
	vec0.push_back(vec);
	cout<<searchMatrix(vec0,3)<<endl;

}