Data Structure Array: Maximum circular subarray sum

 1 #include <iostream>
 2 #include <vector>
 3 #include <algorithm>
 4 #include <queue>
 5 #include <stack>
 6 #include <string>
 7 #include <fstream>
 8 #include <map>
 9 using namespace std;
10 

11 bool allneg(int arr[], int n) {
12     for (int i = 0; i < n; i++) {
13         if (arr[i] > 0) return false;
14     }
15     return true;
16 }
17 
18 int maxsum(int arr[], int n) {
19     int tmp = 0;
20     int ans = INT_MIN;
21     for (int i = 0; i < n; i++) {
22         tmp += arr[i];
23         ans = max(ans, tmp);
24         tmp = max(tmp, 0);
25     }
26     return ans;
27 }
28 
29 int maxcircular(int arr[], int n) {
30     int ans = maxsum(arr, n);
31     if (allneg(arr, n)) return ans;
32     int sum = 0;
33     for (int i = 0; i < n; i++) {
34         sum += arr[i];
35         arr[i] = -arr[i];
36     }
37     return max(ans, sum + maxsum(arr, n));
38 }
39 
40 int main() {
41     int arr[9] = {11, 10, -20, 5, -3, -5, 8, -13, 10};
42     cout << maxcircular(arr, 9) << endl;
43     return 0;
44 }