1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
#include "message.h"
#include "maklib.h"

#include <iostream>

using namespace std;

int main() {
	int n = Size(), nodes = NumberOfNodes();

	if (n < 10) { // too few data to play with nodes..
		nodes = 1;
	} else if (nodes > n / 5) { // more nodes than necessary
		nodes = n / 5;
	}

	if (MyNodeId() >= nodes) {
		// I am useless node :(
		return 0;
	}

	int interval = n / nodes;
	int from = MyNodeId() * interval + 1;
	int to = MyNodeId() == nodes - 1 ? n : (from + interval - 1);

	long long leftSum = 0;
	long long leftMax = -1000000000;

	long long rightSum = 0;
	long long rightMax = -1000000000;

	long long sum = 0;
	long long max = -1000000000;

	for (int i = from; i <= to; ++i) {
		int e = ElementAt(i);

		// Find largest left sum
		leftSum += e;
		if (leftSum > leftMax) {
			leftMax = leftSum;
		}
		
		// Find largest right sum
		rightSum += ElementAt(from + (to - i));
		if (rightSum > rightMax) {
			rightMax = rightSum;
		}
		
		// Find largest element
		if (sum + e > 0) {
			sum = sum + e;
		} else {
			sum = 0;
		}
		if (sum > max) {
			max = sum;
		}
	}

	if (MyNodeId() > 0) {
		PutLL(0, max);
		PutLL(0, leftSum); // total sum == leftSum == rightSum (hope so..)
		PutLL(0, leftMax);
		PutLL(0, rightMax);
		Send(0);
	} else {
		long megaMax = 0;
		rightSum = rightMax;

		if (max > megaMax) {
			megaMax = max;
		}

		for (int i = 1; i < nodes; ++i) {
			Receive(i);
			long long remoteMax = GetLL(i);
			long long remoteSum = GetLL(i);
			long long remoteLeftSum = GetLL(i);
			long long remoteRightSum = GetLL(i);

			if (remoteMax > megaMax) {
				megaMax = remoteMax;
			}
			if (rightSum + remoteLeftSum > megaMax) {
				megaMax = rightSum + remoteLeftSum;
			}

			// Hyrrr na nich!
			if (remoteRightSum > rightSum + remoteSum) {
				rightSum = remoteRightSum;
			} else {
				rightSum += remoteSum;
			}
		}
		cout << megaMax << endl;
	}
	return 0;
}