WTF交换

模拟

题意真麻烦不说了。
用DP模拟题意yy一下加优化就好了，详见代码。

#include<cstdio>
#include<algorithm>
#define fo(i,a,b) for(i=a;i<=b;i++)
#define fd(i,a,b) for(i=a;i>=b;i--)
using namespace std;
const int maxn=3000+10,inf=100000000;
int f[maxn][maxn],re[maxn][maxn];
int a[maxn],id[maxn];
int i,j,k,l,t,n,m,ans;
int mo(int x){
    return (x%n+n)%n;
}
int main(){
    //freopen("t4.in","r",stdin);freopen("t4.out","w",stdout);
    scanf("%d%d",&n,&m);
    fo(i,0,n-1) scanf("%d",&a[i]);
    fo(i,2,n+1)
        fo(j,1,n-1)
            f[i][j]=-inf;
    fo(i,2,n+1){
        t=-inf;
        k=0;
        fo(j,1,n-1){
            f[i][j]=f[i-1][j]+a[mo(j-1-l)]-a[mo(j-l)];
            re[i][j]=j;
            if (t-a[mo(j-l)]>f[i][j]){
                f[i][j]=t-a[mo(j-l)];
                re[i][j]=k;
            }
            if (a[mo(j-1-l)]+f[i-1][j]>t){
                t=a[mo(j-1-l)]+f[i-1][j];
                k=j;
            }
        }
        t=-inf;
        k=0;
        fd(j,n-1,1){
            if (t+a[mo(j-1-l)]>f[i][j]){
                f[i][j]=t+a[mo(j-1-l)];
                re[i][j]=k;
            }
            if (-a[mo(j-l)]+f[i-1][j]>t){
                t=-a[mo(j-l)]+f[i-1][j];
                k=j;
            }
        }
        l=(l+m)%n;
    }
    ans=-inf;
    fo(i,1,n-1)
        if (f[n+1][i]>ans){
            ans=f[n+1][i];
            id[n+1]=i;
        }
    printf("%d\n",ans);
    fd(i,n+1,2)
        id[i-1]=re[i][id[i]];
    fo(i,1,n+1) printf("%d ",id[i]);
    //fclose(stdin);fclose(stdout);
}