74

class Solution {
public:
    bool searchMatrix(vector<vector<int>>& matrix, int target) {
        int n=matrix.size(), m=matrix[0].size(), l=0, r=n*m-1;
        while(l<=r){
            int mid = (l+r)/2;
            int val = matrix[mid/m][mid%m];
            if(val == target)
                return true;
            else if(val < target)
                l = mid+1;
            else
                r = mid-1;
        }
        return false;
    }
};