CodeForces 788A - Functions again [ DP ]

反着求一遍最大连续子序列(前项依赖)

 #include <bits/stdc++.h>
 using namespace std;
 #define LL long long
 const int MAXN = ;
 int n;
 LL dp[MAXN];
 LL a[MAXN];
 LL Cal(int i)
 {
     return abs(a[i] - a[i+]);
 }
 int main()
 {
     scanf("%d", &n);
     for (int i = ; i <= n; i++)
         scanf("%lld", &a[i]);
     memset(dp, , sizeof(dp));
     dp[n-] = Cal(n-);
     LL ans = dp[n-];
     for (int i = n-; i > ; i--)
     {
         dp[i] = max(Cal(i), Cal(i) - dp[i+]);
         if (i < n-)
             dp[i] = max(dp[i], dp[i+] - Cal(i+) + Cal(i) );
         ans = max(dp[i], ans);
     }
     printf("%lld\n", ans);
 }