Question

题目大意: 在一个数组中,找到满足一对元素,可以得到一定条件的最大值(和购买股票是一样的题型)

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

Difficulty:Medium

Category:

Solution

Time complexity: O(n), Space complexity: O(1)

class Solution {
 public:
  int maxScoreSightseeingPair(vector<int>& A) {
    int ans = 0, left = INT_MIN;
    for (int i = 0; i < A.size(); ++i) {
      ans = max(ans, A[i] - i + left);
      left = max(left, A[i] + i);
    }
    return ans;
  }
};