package com.interview.array;
/**
* http://www.geeksforgeeks.org/maximum-contiguous-circular-sum/
* Test cases
* All negative
* All positives
* all 0s
*/
class Triplet{
int start;
int end;
int sum;
@Override
public String toString() {
return "Triplet [start=" + start + ", end=" + end + ", sum=" + sum
+ "]";
}
}
public class KadaneWrapArray {
public Triplet kadaneWrap(int arr[]){
Triplet straightKadane = kadane(arr);
int sum =0;
for(int i=0; i < arr.length; i++){
sum += arr[i];
arr[i] = -arr[i];
}
Triplet wrappedNegKadane = kadane(arr);
for(int i=0; i < arr.length; i++){
arr[i] = -arr[i];
}
if(straightKadane.sum < sum + wrappedNegKadane.sum){
straightKadane.sum = wrappedNegKadane.sum + sum;
straightKadane.start = wrappedNegKadane.end+1;
straightKadane.end = wrappedNegKadane.start-1;
}
return straightKadane;
}
/**
* This method assumes there is at least one positive number in the array.
* Otherwise it will break
* @param arr
* @return
*/
public Triplet kadane(int arr[]){
int sum =0;
int cStart = 0;
int mStart = 0;
int end = 0;
int maxSum = Integer.MIN_VALUE;
for(int i=0; i < arr.length; i++){
sum += arr[i];
if(sum <= 0){
sum = 0;
cStart = i+1;
}else{
if(sum > maxSum){
maxSum = sum;
mStart = cStart;
end = i;
}
}
}
Triplet p = new Triplet();
p.sum = maxSum;
p.start = mStart;
p.end = end;
return p;
}
public static void main(String args[]){
KadaneWrapArray kwa = new KadaneWrapArray();
int input[] = {12, -2, -6, 5, 9, -7, 3};
int input1[] = {8, -8, 9, -9, 10, -11, 12};
System.out.println(kwa.kadaneWrap(input));
System.out.println(kwa.kadaneWrap(input1));
}
}