2016 ACM/ICPC Asia Regional Qingdao Online HDU5883

链接:http://acm.hdu.edu.cn/showproblem.php?pid=5883

解法:先判断是不是欧拉路,然后枚举

#pragma comment(linker, "/STACK:102400000,102400000")
#include <math.h>
#include <time.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <set>
#include <map>
#include <string>
#include <stack>
#include <queue>
#include <vector>
#include <bitset>
#include <iostream>
#include <algorithm>
#define pb push_back
#define fi first
#define se second
#define icc(x) (1<<(x))
#define lcc(x) (1ll<<(x))
#define lowbit(x) (x&-x)
#define debug(x) cout<<#x<<"="<<x<<endl
#define rep(i,s,t) for(int i=s;i<t;++i)
#define per(i,s,t) for(int i=t-1;i>=s;--i)
#define mset(g, x) memset(g, x, sizeof(g))
using namespace std; typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int ui;
typedef double db;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<int> veci;
const int mod=(int)1e9+7,inf=0x3fffffff,rx[]={-1,0,1,0},ry[]={0,1,0,-1};
const ll INF=1ll<<60;
const db pi=acos(-1),eps=1e-8; template<class T> void rd(T &res){
res = 0; int ch,sign=0;
while( (ch=getchar())!='-' && !(ch>='0'&&ch<='9'));
if(ch == '-') sign = 1; else res = ch-'0';
while((ch=getchar())>='0'&&ch<='9') res = (res<<3)+(res<<1)+ch-'0';
res = sign?-res:res;
}
template<class T>void rec_pt(T x){
if(!x)return;
rec_pt(x/10);
putchar(x%10^48);
}
template<class T>void pt(T x){
if(x<0) putchar('-'),x=-x;
if(!x)putchar('0');
else rec_pt(x);
}
template<class T>inline void ptn(T x){ pt(x),putchar('\n'); }
template<class T>inline void Max(T &a,T b){ if(b>a)a=b; }
template<class T>inline void Min(T &a,T b){ if(b<a)a=b; }
template<class T>inline T mgcd(T b,T d){ return b?mgcd(d%b,b):d; }//gcd模板,传入的参数必须是用一类型
//-------------------------------主代码--------------------------------------// int g[100100];
int d[100100];
int markpath[100100];
int mark[100100]; struct node{
int to,next;
}edge[1000100]; int cnt,pre[100100]; void add_edge(int u,int v){
edge[cnt].to = v;
edge[cnt].next = pre[u];
pre[u] = cnt++;
} void dfs(int s){
mark[s] = 1;
for(int p=pre[s];p!=-1;p=edge[p].next){
int v = edge[p].to;
if(mark[v] == 1) continue;
dfs(v);
}
} int main()
{
int T;
rd(T);
while (T--) {
cnt = 0;
mset(d, 0); mset(markpath, 0); mset(pre, -1); mset(mark, 0);
int n,m;
rd(n),rd(m);
for(int i=1;i<=n;i++)
{
rd(g[i]);
}
rep(i, 0, m){
int x,y;
rd(x),rd(y);
markpath[x] = 1; markpath[y] = 1;
add_edge(x,y);
add_edge(y,x);
d[x]++; d[y]++;
}
int cnt = 0;
for(int i=1;i<=n;i++){
if(d[i]%2 != 0) cnt++;
} if(cnt!=0 && cnt!=2){
printf("Impossible\n");
continue;
}
int flag = 0;
for(int i=1;i<=n;i++){
if(markpath[i]==1 && mark[i] ==0){
flag ++;
dfs(i);
}
}
if(flag > 1) {
printf("Impossible\n");
continue;
} int ans = 0; if(cnt == 0){
int sum = 0;
for(int i=1;i<=n;i++){
if( (d[i]/2)%2!=0 )
{
sum ^= g[i];
}
}
for(int i=1;i<=n;i++){
if(markpath[i]==1)
ans = max(ans,sum^g[i]);
}
}else{
int sum = 0;
for(int i=1;i<=n;i++){
if(d[i]%2!=0){
d[i]++;
}
if( (d[i]/2)%2!=0 )
{
sum ^= g[i];
}
}
ans = sum;
}
ptn(ans);
}
return 0;
}

  

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