Sorting is `O(n log n)`

. The rest is `O(n)`

.

Here, `A = houses`

and `H = heaters`

.

```
class Solution {
public:
/*
Example: h = house, * = heater M = INT_MAX
h h h h h h h h h houses
1 2 3 4 5 6 7 8 9 index
* * * heaters
0 2 1 0 1 0 - - - (distance to nearest RHS heater)
0 1 2 0 1 0 1 2 3 (distance to nearest LHS heater)
0 1 1 0 1 0 1 2 3 (res = minimum of above two)
Result is maximum value in res, which is 3.
*/
int findRadius(vector<int>& A, vector<int>& H) {
sort(A.begin(), A.end());
sort(H.begin(), H.end());
vector<int> res(A.size(), INT_MAX);
// For each house, calculate distance to nearest RHS heater
for (int i = 0, h = 0; i < A.size() && h < H.size(); ) {
if (A[i] <= H[h]) { res[i] = H[h] - A[i]; i++; }
else { h++; }
}
// For each house, calculate distance to nearest LHS heater
for (int i = A.size()-1, h = H.size()-1; i >= 0 && h >= 0; ) {
if (A[i] >= H[h]) { res[i] = min(res[i], A[i] - H[h]); i--; }
else { h--; }
}
return *max_element(res.begin(), res.end());
}
};
```