今天这场打的还不错吧,就是开场一个小时就WA在两道水题上了,今天的题总体上比原先的个人赛水多了,有点喜剧性吧,就
像这个一样
,其实我也挺喜欢听小苹果的,虽然一开始骂这是一首破歌。
今天看到A题CodeForces 205B,好开心,这不是可以用昨天那道ZOJ 2243 treap用线段树解决的方法解决。开心的打完代码,
想着我实在太聪明了,可是,但我提交的时候发现,好吧,我又把一道题复杂话了,WA了,一时找不到bug,去
码CUVA 11452题水题,又WA,后来一开窍,C、A题BUG瞬间找出,接着HLightOJ 1148/BLightOJ 1277/DCodeForces 284C都是WA了后才过,
看来我今天不宜做题,最后终于yyG题CodeForces 388C、CodeForces 388C题,1y过了。
看F题UVA 11301,dp?没想法。 最大流,咦,好像可以,建图,比赛没过,赛后补过。
重点讲讲F题,F题可以DP,可以最小费用最大流,DP貌似是正解,像我这种渣渣就来讲讲歪解吧。
把图中每个点拆成两个点,流量为1,费用为原图点的权值。相邻的点连一条边,费用为0,流量为1.
一个起点s连向3个点@,流量为1,费用为0,
原矩阵中最后一列的点连向终点t,流量为INF,费用为0。
具体看代码:
view code#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <vector>
#include <cmath>
#include <map>
using namespace std;
typedef long long ll;
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
const int INF = 1<<30;
const int N = 1010;
const int M = N*15;
int _, cas=1, n, m, s, t;
char str[5][N];
bool inq[M];
int d[M];
int p[M];
int a[M];
int pre[M];
struct edge
{
int u, v, cap,cost, next;
edge() {}
edge(int u, int v, int cap,int cost, int next):u(u),v(v),cap(cap),cost(cost),next(next) {}
}e[200*N];
int ecnt = 0;
int getid(int x, int y)
{
return x*n+y+1;
}
void addedge(int u,int v, int cap, int cost)
{
e[ecnt] = edge(u, v, cap, cost, pre[u]);
pre[u] = ecnt++;
e[ecnt] = edge(v, u, 0, -cost, pre[v]);
pre[v] = ecnt++;
}
bool BellmanFort(int &flow, int &cost)
{
for(int i=s; i<=t; i++) d[i] = INF;
memset(inq, 0, sizeof(inq));
d[s] = 0; p[s] = 0; a[s] = INF;
queue<int >q;
q.push(s);
while(!q.empty())
{
int u = q.front(); q.pop();
inq[u] = 0;
for(int i=pre[u]; ~i; i=e[i].next)
{
int v = e[i].v;
if(e[i].cap>0 && d[v]>d[u]+e[i].cost)
{
d[v] = d[u] + e[i].cost;
p[v] = i;
a[v] = min(a[u], e[i].cap);
if(!inq[v])
{
q.push(v);
inq[v] = 1;
}
}
}
}
if(d[t]==INF) return false;
flow += a[t];
cost += d[t]*a[t];
int u = t;
while(u!=s)
{
e[p[u]].cap -= a[t];
e[p[u]^1].cap += a[t];
u = e[p[u]].u;
}
return true;
}
int Mincost()
{
int flow = 0, cost = 0;
while(BellmanFort(flow, cost)) ;
return cost;
}
void solve()
{
for(int i=0; i<5; i++) scanf("%s", str[i]);
ecnt = 0;
int B = getid(4,n-1)+1;
s = 0, t = getid(5,0)+B;
memset(pre, -1, sizeof(pre));
for(int i=0; i<5; i++)
{
if(str[i][0]=='@') addedge(s, getid(i, 0), 1, 0);
for(int j=0; j<n; j++)
{
if(str[i][j]=='@') addedge(getid(i, j), getid(i,j)+B, 1, 0);
else addedge(getid(i, j), getid(i,j)+B, 1, str[i][j]-'0');
if(i>0) addedge(getid(i, j)+B, getid(i-1, j), 1, 0);
if(i<4) addedge(getid(i, j)+B, getid(i+1, j), 1, 0);
if(j<n-1) addedge(getid(i, j)+B, getid(i, j+1), 1, 0);
if(j>0) addedge(getid(i, j)+B, getid(i, j-1), 1, 0);
}
addedge(getid(i,n-1)+B, t, INF, 0);
}
cout<<Mincost()<<endl;
}
int main()
{
// freopen("in.txt", "r", stdin);
while(scanf("%d", &n)>0 && n) solve();
return 0;
}
B题:LightOJ 1277 LIS+贪心
view code#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <queue>
#include <vector>
#include <cmath>
#include <map>
using namespace std;
typedef long long ll;
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
const int INF = 1<<30;
const int N = 100010;
int _, cas=1, n, m, len;
int a[N], g[N], d[N], num[N];
int res[N], cnt;
int find(int x)
{
int l = 1, r = n, ans = 0;
while(l<=r)
{
int m = (l+r)>>1;
if(g[m]<=x) ans = m, r = m-1;
else l = m+1;
}
return ans;
}
void init()
{
for(int i=1; i<=n; i++) g[i] = -INF;
for(int i=n; i>0; i--)
{
int k = find(a[i]);
// printf("%d : %d\n", i, k);
d[i] = k;
g[k] = a[i];
}
}
bool calc()
{
cnt = 0;
int now = len, pre=-INF;
for(int i=1; i<=n; i++)
{
if(d[i]>=now && a[i]>pre)
{
res[cnt++] = a[i];
now--;
if(now==0) break;
pre = a[i];
}
}
if(cnt<len) return 0;
for(int i=0; i<cnt; i++)
{
if(i) printf(" ");
printf("%d", res[i]);
}
printf("\n");
return 1;
}
void solve()
{
scanf("%d%d", &n, &m);
int L = INF, R=-INF;
for(int i=1; i<=n; i++)
{
scanf("%d", a+i);
if(L>a[i]) L = a[i];
if(R<a[i]) R = a[i];
}
printf("Case %d:\n", cas++);
init();
while(m--)
{
scanf("%d", &len);
if(!calc()) puts("Impossible");
}
}
int main()
{
// freopen("in", "r", stdin);
cin>>_;
while(_--)
solve();
return 0;
}
G题 CodeForces 388C 贪心,
view code#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
typedef long long ll;
const int N = 200;
int n, m,a[N];
int main()
{
while(scanf("%d", &n)>0)
{
int v, num, suma = 0, sumb = 0, cnt = 0;
for(int i=0; i<n; i++)
{
scanf("%d", &num);
int mid = (num+1)/2;
for(int j=1; j<=num; j++)
{
scanf("%d", &v);
if((num&1) && mid==j) a[cnt++] = v;
else
{
if(j<=mid) suma += v;
else sumb += v;
}
}
}
sort(a, a+cnt);
int f = 1;
for(int i=cnt-1; i>=0; i--)
{
if(f) suma += a[i];
else sumb += a[i];
f ^= 1;
}
printf("%d %d\n", suma, sumb);
}
return 0;
}