Search a 2D Matrix

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