Leetcode: Best Sightseeing Pair

Best Sightseeing Pair



Similar Problems:


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

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.


  • Solution:
// Blog link: https://code.dennyzhang.com/best-sightseeing-pair
// Basic Ideas:
//    Compose two new arrays: l1 and l2
//    l1[i] = A[i]+i
//    l2[j] = A[j]-j
//    l1 is non decreasing array
// Complexity: Time O(n)), Space O(n)
func maxScoreSightseeingPair(A []int) int {
    l1, l2 := make([]int, len(A)), make([]int, len(A))
    for i, v := range A{
        l1[i], l2[i] = v+i, v-i
    }
    // result can't be smaller than 0
    res := 0
    maxA := l1[0]
    for i:=1; i<len(A); i++ {
        if res < maxA+l2[i] {
            res = maxA+l2[i]
        }
        if l1[i] > maxA {
            maxA = l1[i]
        }
    }
    return res
}
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