loj2042 「CQOI2016」不同的最小割

分治+最小割
看到题解的第一句话是这个就秒懂了,然后乱七八糟的错误、越界、RE……

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
int n, m, uu, vv, ww, hea[855], cnt, a[855], ss, tt, lev[855], tmp[855], cur[855];
int maxFlow;
const int oo=0x3f3f3f3f;
queue d;
set se;
struct Edge{
    int too, nxt, val;
}edge[17005];
void add_edge(int fro, int too, int val){
    edge[cnt].nxt = hea[fro];
    edge[cnt].too = too;
    edge[cnt].val = val;
    hea[fro] = cnt++;
}
bool bfs(){
    memset(lev, 0, sizeof(lev));
    lev[ss] = 1;
    d.push(ss);
    while(!d.empty()){
        int x=d.front();
        d.pop();
        for(int i=hea[x]; i!=-1; i=edge[i].nxt){
            int t=edge[i].too;
            if(!lev[t] && edge[i].val>0){
                lev[t] = lev[x] + 1;
                d.push(t);
            }
        }
    }
    return lev[tt]!=0;
}
int dfs(int x, int lim){
    if(x==tt)   return lim;
    int addFlow=0;
    for(int &i=cur[x]; i!=-1; i=edge[i].nxt){
        int t=edge[i].too;
        if(lev[t]==lev[x]+1 && edge[i].val>0){
            int tmp=dfs(t, min(lim-addFlow, edge[i].val));
            edge[i].val -= tmp;
            edge[i^1].val += tmp;
            addFlow += tmp;
            if(addFlow>=lim)    break;
        }
    }
    return addFlow;
}
void dinic(){
    maxFlow = 0;
    while(bfs()){
        for(int i=1; i<=n; i++)
            cur[i] = hea[i];
        maxFlow += dfs(ss, oo);
    }
}
void solve(int l, int r){
    if(l>=r)    return ;
    for(int i=0; i> 1;
    ss = a[l]; tt = a[r];
    dinic();
    se.insert(maxFlow);
    int pu=l, pv=r;
    for(int i=l; i<=r; i++)
        if(lev[a[i]])
            tmp[pu++] = a[i];
        else
            tmp[pv--] = a[i];
    for(int i=l; i<=r; i++)
        a[i] = tmp[i];
    solve(l, pu-1);
    solve(pv+1, r);
}
int main(){
    memset(hea, -1, sizeof(hea));
    cin>>n>>m;
    for(int i=1; i<=m; i++){
        scanf("%d %d %d", &uu, &vv, &ww);
        add_edge(uu, vv, ww);
        add_edge(vv, uu, ww);
    }
    for(int i=1; i<=n; i++)
        a[i] = i;
    solve(1, n);
    cout<

转载于:https://www.cnblogs.com/poorpool/p/8945452.html

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