Write an efficient algorithm that searches for a value in an m x n matrix. This matrix has the following PRoperties:

For example,

Consider the following matrix:

[  [1,   3,  5,  7],  [10, 11, 16, 20],  [23, 30, 34, 50]]
Given target = 3, return true.
answer:
class Solution {public:    bool searchMatrix(vector<vector<int>>& matrix, int target) {        int m = matrix.size();        if(m == 0) return false;        int n = matrix[0].size();        if(n == 0) return false;        int mLeft = 0, mRight = m - 1, nLeft = 0, nRight = n - 1;        int mMid = 0, nMid = 0;        while(mLeft <= mRight){            mMid = (mLeft + mRight) / 2;            nMid = (nLeft + nRight) / 2;            if(matrix[mMid][nMid] > target){                if(matrix[mMid][0] > target) mRight = mMid - 1;                else if(matrix[mMid][0] < target) break;                else return true;            }            else if(matrix[mMid][nMid] < target){                if(matrix[mMid][n - 1] > target) break;                else if(matrix[mMid][n - 1] < target) mLeft = mMid + 1;                else return true;            }             else return true;        }        if(mLeft > mRight) return false;                while(nLeft <= nRight){            nMid = (nLeft + nRight) / 2;            if(matrix[mMid][nMid] < target) nLeft = nMid + 1;            else if(matrix[mMid][nMid] > target) nRight = nMid - 1;            else return true;        }        return false;    }};