标签：一个 memset IV term range tip common about fine
Description
The galaxy war between the Empire Draco and the Commonwealth of Zibu broke out 3 years ago. Draco established a line of defense called Grot. Grot is a straight line with N defense stations. Because of the cooperation of the stations, Zibu’s Marine Glory cannot march any further but stay outside the line.
A mystery Information Group X benefits form selling information to both sides of the war. Today you the administrator of Zibu’s Intelligence Department got a piece of information about Grot’s defense stations’ arrangement from Information Group X. Your task is to determine whether the information is reliable.
The information consists of M tips. Each tip is either precise or vague.
Precise tip is in the form of P A B X, means defense station A is X light-years north of defense station B.
Vague tip is in the form of V A B, means defense station A is in the north of defense station B, at least 1 light-year, but the precise distance is unknown.
Input
There are several test cases in the input. Each test case starts with two integers N (0 < N ≤ 1000) and M (1 ≤ M ≤ 100000).The next M line each describe a tip, either in precise form or vague form.
Output
Output one line for each test case in the input. Output “Reliable” if It is possible to arrange N defense stations satisfying all the M tips, otherwise output “Unreliable”.
Sample Input
3 4
P 1 2 1
P 2 3 1
V 1 3
P 1 3 1
5 5
V 1 2
V 2 3
V 3 4
V 4 5
V 3 5
Sample Output
Unreliable
Reliable
Solution：
还是差分约束判断可行性。。。
我们依然罗列出约束条件（可行性我直接当做求最小值来做）：
1、$s[v]-s[u]=c,s[u]-s[v]=c$，所以建边$w[u,v]=w[v,u]=c$（注意是双向的，因为等于是个对于两边都成立的约束条件）
2、$s[v]-s[u]>0$，即$s[v]-s[u]\geq 1$，所以建边$w[u,v]=1$
记得新建一个源点，连向各点$w[1,i]=0,\;i\in 1\rightarrow n$，以保证图联通。
然后跑一遍最长路，判断一下有无环输出就好了。
代码：
1 #include<iostream> 2 #include<cstdio> 3 #include<cstring> 4 #include<queue> 5 #pragma GCC optimize(2) 6 #define il inline 7 #define For(i,a,b) for(int (i)=(a);(i)<=(b);(i)++) 8 using namespace std; 9 const int N=300005,M=1005,inf=23333333; 10 int h[M],to[N],net[N],w[N],cnt,dis[M],tot[M],n,m; 11 bool vis[M]; 12 13 il void add(int u,int v,int c){to[++cnt]=v,net[cnt]=h[u],h[u]=cnt,w[cnt]=c;} 14 15 il void gi(int &a){ 16 a=0;char x=getchar();bool f=0; 17 while((x<‘0‘||x>‘9‘)&&x!=‘-‘)x=getchar(); 18 if(x==‘-‘)x=getchar(),f=1; 19 while(x>=‘0‘&&x<=‘9‘)a=(a<<3)+(a<<1)+x-48,x=getchar(); 20 } 21 22 il bool spfa(){ 23 queue<int>q; 24 dis[0]=0;q.push(0);tot[0]++; 25 while(!q.empty()){ 26 int u=q.front();q.pop();vis[u]=0; 27 for(int i=h[u];i;i=net[i]) 28 if(dis[to[i]]<dis[u]+w[i]){ 29 dis[to[i]]=dis[u]+w[i]; 30 if(!vis[to[i]]){ 31 if(++tot[to[i]]>n)return 0; 32 q.push(to[i]),vis[to[i]]=1; 33 } 34 } 35 } 36 return 1; 37 } 38 39 int main(){ 40 while(~scanf("%d%d",&n,&m)){ 41 char s[5]; 42 cnt=0; 43 memset(dis,-0x3f,sizeof(int)*(n+3)); 44 memset(vis,0,sizeof(int)*(n+3)); 45 memset(tot,0,sizeof(int)*(n+3)); 46 memset(h,0,sizeof(h)); 47 int u,v,c; 48 while(m--){ 49 scanf("%s",s); 50 gi(u),gi(v); 51 if(s[0]==‘P‘){ 52 gi(c); 53 add(v,u,-c);add(u,v,c); 54 } 55 else add(u,v,1); 56 } 57 For(i,1,n) add(0,i,0); 58 if(spfa())puts("Reliable"); 59 else puts("Unreliable"); 60 } 61 return 0; 62 }
POJ 2983-Is the Information Reliable
标签：一个 memset IV term range tip common about fine
原文地址：https://www.cnblogs.com/five20/p/9177055.html
