网络流不用动脑子的好爽啊
#include <iostream>
#include <cstring>
#include <cstdio>
#include <queue>
using namespace std;
int n, uu, hea[105], cnt, ss, tt, sum, minCost, pre[105], dis[105];
const int oo=0x3f3f3f3f;
bool vis[105];
queue<int> d;
struct Edge{
int too, nxt, val, cst;
}edge[805];
void add_edge(int fro, int too, int val, int cst){
edge[cnt].nxt = hea[fro];
edge[cnt].too = too;
edge[cnt].val = val;
edge[cnt].cst = cst;
hea[fro] = cnt++;
}
void addEdge(int fro, int too, int val, int cst){
add_edge(fro, too, val, cst);
add_edge(too, fro, 0, -cst);
}
bool spfa(){
memset(dis, 0x3f, sizeof(dis));
memset(pre, -1, sizeof(pre));
dis[ss] = 0;
d.push(ss);
vis[ss] = true;
while(!d.empty()){
int x=d.front();
d.pop();
vis[x] = false;
for(int i=hea[x]; i!=-1; i=edge[i].nxt){
int t=edge[i].too;
if(dis[t]>dis[x]+edge[i].cst && edge[i].val>0){
dis[t] = dis[x] + edge[i].cst;
pre[t] = i;
if(!vis[t]){
vis[t] = true;
d.push(t);
}
}
}
}
return dis[tt]!=oo;
}
void f(){
while(spfa()){
int tmp=oo;
for(int i=pre[tt]; i!=-1; i=pre[edge[i^1].too])
tmp = min(tmp, edge[i].val);
for(int i=pre[tt]; i!=-1; i=pre[edge[i^1].too]){
edge[i].val -= tmp;
edge[i^1].val += tmp;
minCost += tmp * edge[i].cst;
}
}
}
int main(){
memset(hea, -1, sizeof(hea));
cin>>n;
ss = 0; tt = n + 1;
for(int i=1; i<=n; i++){
scanf("%d", &uu);
addEdge(ss, i, uu, 0);
sum += uu;
}
sum /= n;
for(int i=1; i<=n; i++){
addEdge(i, tt, sum, 0);
if(i>1) addEdge(i, i-1, oo, 1);
if(i<n) addEdge(i, i+1, oo, 1);
}
addEdge(1, n, oo, 1);
addEdge(n, 1, oo, 1);
f();
cout<<minCost<<endl;
return 0;
}