class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int m = matrix.size();
        int n = matrix[0].size();

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

        return false;
    }
};