Leetcode: Search a 2D Matrix

http://oj.leetcode.com/problems/search-a-2d-matrix/

Take the matrix as a sorted list, and then use binary search directly.

class Solution {
public:
    int GetValue(vector<vector<int> > &matrix, int index){
        int col=matrix[0].size();
        int c=index%col;
        int r=index/col;
        return matrix[r][c];
    }
    bool searchMatrix(vector<vector<int> > &matrix, int target) {
        if(matrix.size()==0) return false;
        int row=matrix.size(), col=matrix[0].size();
        int left=0, right=row*col-1;
        while(left<=right){
            int mid=(left+right)/2;
            int value=GetValue(matrix,mid);
            if(value==target) return true;
            else if(value<target) left=mid+1;
            else right=mid-1;
        }
        return false;
    }
};