Maximum sum Bi-tonic Sub-sequence
Given an array of integers. A subsequence of arr[] is called Bitonic if it is first increasing, then decreasing.
Examples :
Input : arr[] = {1, 15, 51, 45, 33,
100, 12, 18, 9}
Output : 194
Explanation : Bi-tonic Sub-sequence are :
{1, 51, 9} or {1, 50, 100, 18, 9} or
{1, 15, 51, 100, 18, 9} or
{1, 15, 45, 100, 12, 9} or
{1, 15, 45, 100, 18, 9} .. so on
Maximum sum Bi-tonic sub-sequence is 1 + 15 +
51 + 100 + 18 + 9 = 194
Input : arr[] = {80, 60, 30, 40, 20, 10}
Output : 210
class Solution {
public int MaxSumBS(int arr[], int n) {
int max_sum = Integer.MIN_VALUE;
// MSIBS[i] ==> Maximum sum Increasing Bi-tonic
// subsequence ending with arr[i]
// MSDBS[i] ==> Maximum sum Decreasing Bi-tonic
// subsequence starting with arr[i]
// Initialize MSDBS and MSIBS values as arr[i] for
// all indexes
int MSIBS[] = new int[n];
int MSDBS[] = new int[n];
for (int i = 0; i < n; i++) {
MSDBS[i] = arr[i];
MSIBS[i] = arr[i];
}
// Compute MSIBS values from left to right */
for (int i = 1; i < n; i++)
for (int j = 0; j < i; j++)
if (arr[i] > arr[j] && MSIBS[i] < MSIBS[j] + arr[i])
MSIBS[i] = MSIBS[j] + arr[i];
// Compute MSDBS values from right to left
for (int i = n - 2; i >= 0; i--)
for (int j = n - 1; j > i; j--)
if (arr[i] > arr[j] && MSDBS[i] < MSDBS[j] + arr[i])
MSDBS[i] = MSDBS[j] + arr[i];
// Find the maximum value of MSIBS[i] +
// MSDBS[i] - arr[i]
for (int i = 0; i < n; i++)
max_sum = Math.max(max_sum, (MSDBS[i] + MSIBS[i] - arr[i]));
// return max sum of bi-tonic
// sub-sequence
return max_sum;
}
}
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