class Solution {public:    bool searchMatrix(vector
    
     
       > &matrix, int target) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        if(matrix.empty()) return false;                int M = matrix.size();        int N = matrix[0].size();                int i = 0, j = N-1;                while( i < M && j >=0){            if(matrix[i][j] == target) return true;            else if(matrix[i][j] < target) i++;            else j--;        }        return false;            }};