Codeforces731E Funny Game

dp[i][0]表示从i出发，轮到先手走的最优值。

dp[i][1]表示从i出发，轮到后手走的最优值。

dp[i][0]=max(dp[j][1]+sum[j])

dp[i][1]=min(dp[j][0]-sum[j])

倒着推就好了。

#include <bits/stdc++.h>
using namespace std;

int a[200010];
int dp[200010][2];
int sum[200010];

int main()
{
    int n;
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
        scanf("%d", a + i), sum[i] = sum[i - 1] + a[i];
    int houShouMax = sum[n], xianShouMin = -sum[n];
    for (int i = n - 1; i >= 1; i--)
    {
        dp[i][0] = houShouMax;
        dp[i][1] = xianShouMin;
        houShouMax = max(houShouMax, dp[i][1] + sum[i]);
        xianShouMin = min(xianShouMin, dp[i][0] - sum[i]);
    }
    printf("%d", dp[1][0]);
    return 0;
}