[LeetCode] Search a 2D Matrix

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

果不其然的一遍过，在循环的时候保持区间内必须有3个及以上的数，然后退出循环后再判断是个好方法~