Search a 2D Matrix

LeetCode #74

Description:

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.

Example:

Consider the following matrix:

[
  [1,   3,  5,  7],
  [10, 11, 16, 20],
  [23, 30, 34, 50]
]
Given target = 3, return true.

Idea:

Code:

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        if(matrix.empty()) return false;

        int M = matrix.size();
        int N = matrix[0].size();
        int i=0;
        int j=N-1;
        while(i<M && j>-1){
            if(matrix[i][j] == target){
                return true;
            }
            else if(matrix[i][j] < target){
                i++;
            }
            else{
                j--;
            }
        }

        return false;
    }
};