Best Sightseeing Pair

Given an array A of positive integers, A[i] represents the value of the i-th sightseeing spot, and two sightseeing spots i and j have distance j - i between them.

The score of a pair (i < j) of sightseeing spots is (A[i] + A[j] + i - j) : the sum of the values of the sightseeing spots, minus the distance between them.

Return the maximum score of a pair of sightseeing spots.

 

Example 1:

Input: [8,1,5,2,6]
Output: 11
Explanation: i = 0, j = 2, A[i] + A[j] + i - j = 8 + 5 + 0 - 2 = 11
 

Note:

  1. 2 <= A.length <= 50000
  2. 1 <= A[i] <= 1000

Solution:

class Solution {
    public int maxScoreSightseeingPair(int[] A) {
        //       [8, 1, 5, 2, 6] 
        // res [] -1 9 11  7 10 
        // maxI[] 7  6  5  4  5
        int maxI = A[0] - 1;
        int res = -1;
        for (int j = 1; j < A.length; j ++) {
            res = Math.max(res, A[j] + maxI);
            maxI = Math.max(maxI - 1, A[j] - 1);
        }
        return res;
    }
}