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