# 74. Search a 2D Matrix
98.74%，对二维数组进行二分查找。
- 将二维数组看作一维数组
- 通过整除和取模得到
mid在二维数组的下标 - 再进行普通的二分查找，可以用循环，也可以递归。
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();
return binSearch(0, n * m - 1, target, matrix, n);
}
bool binSearch(int left, int right, int &target, vector<vector<int>> &matrix, int &n) {
if (left > right) return false;
int mid = (left + right) / 2;
int midRow = mid / n, midCol = mid % n;
if (matrix[midRow][midCol] < target)
return binSearch(mid + 1, right, target, matrix, n);
else if (matrix[midRow][midCol] > target)
return binSearch(left, mid - 1, target, matrix, n);
else return true;
}
};
