search-a-2d-matrix

题目描述

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

class Solution {
public:
    bool searchMatrix(vector<vector<int>> &matrix, int target) {
        if(matrix.size() == 0) return false;
        
        int m = matrix.size();
        int n = matrix[0].size();
        
  
        int index = -1;
        for(int i =0;i<m;i++){
            if(matrix[i][n-1] >= target)
            {
                index = i;
                break;
            }
        }
        if(index == -1)return false;
        
        for(int j = 0;j<=n-1;j++){
            if(matrix[index][j]==target)
                return true;
        }
        return false;
    }
};

 

true.