2017 Multi-University Training Contest

2017 Multi-University Training Contest - Team 3

04 / hdu6058    链表好题

题意：求所有区间第 k 大的和。

tags： 好像不用链表，暴力都可以。。。

#include<bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/STACK:102400000,102400000")
#define rep(i,a,b) for (int i=a; i<=b; ++i)
#define per(i,b,a) for (int i=b; i>=a; --i)
#define mes(a,b)  memset(a,b,sizeof(a))
#define INF 0x3f3f3f3f
#define MP make_pair
#define PB push_back
#define fi  first
#define se  second
typedef long long ll;
const int N = 500005;

int n, k, a[N], pre[N], nex[N], pos[N], num1[100], num2[200];
ll  cal(int p)
{
    ll  res = 0;
    int c1=0, c2=0;
    for(int i=p; i>0 && c1<k; i=pre[i]) {
        num1[++c1] = i - pre[i];
    }
    for(int i=p; i<=n && c2<k; i=nex[i]) {
        num2[++c2] = nex[i] - i;
    }
    for(int i=c1,j=1; i>0 && j<=c2; )
    {
        if(i+j-1!=k) { ++j; continue; }
        res += num1[i]*num2[j];
        --i, ++j;
    }   
    return res;
}
void Del(int p)
{
    nex[pre[p]] = nex[p];
    pre[nex[p]] = pre[p];
}
int main()
{
    int T;  scanf("%d", &T);
    while(T--)
    {
        scanf("%d%d", &n, &k);
        rep(i,1,n)
        {
            scanf("%d", &a[i]);
            pos[a[i]] = i;
            pre[i] = i-1, nex[i] = i+1;
        }
        ll  ans = 0;
        rep(i,1,n)
        {
            ans += cal(pos[i])*i;
            Del(pos[i]);
        }
        printf("%lld
", ans);
    }

    return 0;
}

05   dfs，size[]与 k 判一下就好。

#include<bits/stdc++.h>
using namespace std;
#pragma comment(linker, "/STACK:102400000,102400000")
#define rep(i,a,b) for (int i=a; i<=b; ++i)
#define per(i,b,a) for (int i=b; i>=a; --i)
#define mes(a,b)  memset(a,b,sizeof(a))
#define INF 0x3f3f3f3f
#define MP make_pair
#define PB push_back
#define fi  first
#define se  second
typedef long long ll;
const int N = 1000005;

int n, k;
ll  ans;
struct Edge{int to,next,w; }e[N<<1];
int tot, head[N], Size[N];
void Addedge(int u, int v, int w) { e[tot]={v,head[u],w }; head[u]=tot++; }
void dfs(int u, int fa)
{
    Size[u] = 1;
    for(int i=head[u]; i!=-1; i=e[i].next)
        if(e[i].to!=fa)
    {
        int to=e[i].to, w=e[i].w;
        dfs(to, u);
        Size[u] += Size[to];
        ans += 1LL*min(Size[to], k)*w;
    }
}
void Init()
{
    mes(head, -1);  mes(Size, 0);
    tot=0,  ans=0;
}
int main()
{
    while(~scanf("%d %d", &n, &k))
    {
        Init();
        int u, v, w;
        rep(i,1,n-1)
        {
            scanf("%d %d %d", &u, &v, &w);
            Addedge(u, v, w);  Addedge(v, u, w);
        }
        dfs(1, 0);
        printf("%lld
", ans);
    }

    return 0;
}