Leetcode 1911. maximum subsequence alternating sum

LeetCode 1911. Maximum subsequence alternating sum

State machine DP

typedef long long LL;
const int N = 1e5 + 10;
class Solution {
    
public:
    LL f[N][2]; //f[i][0] Before presentation i Choose the maximum sum of even numbers ,f[i][1] Before presentation i Select the maximum sum of odd numbers 
    long long maxAlternatingSum(vector<int>& nums) {
    
        int n = nums.size();
        f[0][0] = 0;
        for(int i = 1; i <= n; i ++)
        {
    
            f[i][0] = max(f[i - 1][0], f[i - 1][1] + nums[i - 1]);
            f[i][1] = max(f[i - 1][1], max(0LL, f[i - 1][0] - nums[i - 1]));
        }
        return max(f[n][0], f[n][1]);
    }
};