First, find the row which might have the target. This is the same as "Search Insert Position": the position minus one is the row number;

Second, find the target in this row.

```
class Solution {
public:
bool searchMatrix(vector<vector<int>>& matrix, int target) {
int n = matrix.size();
int m = matrix[0].size();
int l = 0, r = n - 1, k;
if (target < matrix[0][0]) { //If the target is less than the first element, abort immediately.
return false;
}
while (l <= r) {
k = l + ((r - l) >> 1);
if (matrix[k][0] > target) {
r = k - 1;
} else if (matrix[k][0] < target) {
l = k + 1;
} else {
return true;
}
}
k = l + ((r - l + 1) >> 1) - 1; //The inserting position minus one: the row which might have the target
int mid;
l = 0; r = m - 1;
while (l <= r) {
mid = l + ((r - l) >> 1);
if (matrix[k][mid] > target) {
r = mid - 1;
} else if (matrix[k][mid] < target) {
l = mid + 1;
} else {
return true;
}
}
return false;
}
};
```