[Usaco07feb] Silver Bull Party Cow

Title Description

Winter vacation arrived, N cattle are going to a party numbered X (1≤x≤n) of the farm held by the parties (1≤n≤1000), between the farm there is M (1≤m≤100000) Strips of road, each road long Ti (1≤ti≤100).

Every cow must go home after the party, whether it is to go to a party or go home, each cow will choose the shortest path, the shortest path of the N cattle (a round trip) the longest path length.

Input/output format

Input format:

First row of three integers n,m, X;

The second line to line m+1: There are three integers per line Ai,bi, TI, indicates that there is a road from Ai Farm to Bi Farm, the length of ti.

Output format:

An integer that represents the longest shortest short length.

Input/Output sample

Input Sample # #:

4 8 21 2 41 3 21 4 72 1 12 3 53 1 23 4 44 2 3

Sample # # of output:

10

Exercises

It's really a water problem.

As long as the shortest way to build a positive, reverse map can be

Code:

#include <bits/stdc++.h> #pragma GCC optimize (3) namespace zdy{#define RES Register #define RI Res int #defin e ll long long #define DB double #define SHT short #define IL inline #define MB template <class t> #d Efine Fur (i,x,y) for (RI i=x;i<=y;i++) #define FUR (I,x,y) for (i=x;i<=y;i++) #define FDR (i,x,y) for (RI i=x;i>    =y;i--) #define IN2 (x, y) in (x), in (y) #define in3 (Z, z) in2 (x, y) #define IN4 (a,b,c,d) in2 (A, b); in2 (c,d) #define OUTN (x) out (x), PC (' \ n ') #define CLR (x, y) memset (x,y,sizeof) #define CPY (x, y) memcpy (x,y,sizeof) #de Fine FL (i,x) for (RI i=head[x],to;to=e[i].to,i;i=e[i].nxt) #define INF 2147483630 #define FIN (s) freopen (S ".", "R", s Tdin) #define FOUT (s) freopen (S ". Out", "w", stdin) #define GT IO.GC () #define L2 (N) (log (n)/log (2)) MB il T ABS (    T x) {return x>0?x:-x;}    MB il t MAX (t x,t y) {return x>y?x:y;}    MB il t MIN (t x,t y) {return x<y?x:y;} MB il t GCD (t x,t y) {return y?    GCD (y,x%y): x;} MB il void SWAP (t x,t y) {T t=x;y=t;x=y;}} Using namespace zdy;using namespace Std;class io{#define FOK (ch!=eof) #define SEP (ch== "| | ch== ' \ n ' | | ch== ' \ t ') #define DSEP!isdigit (CH) #define NEQ (A, a) ((a)-(b) >1e-6) Char Rbuf[1<<20],wbuf[1<<20],b,*p   1,*P2;   int rs,ws,s;       Public:io ():p 1 (rbuf), p2 (wbuf), S (1000000), RS (1000000), WS ( -1), B (1) {} ~io () {fwrite (wbuf,1,ws+1,stdout);} Il char GC () {return rs==s&& (P1=rbuf,rs=-1, (S=fread (Rbuf,1,s+1,stdin)-1) ==-1)? (       b=0,eof):(++rs,*p1++);}       Il void pc (int x) {ws==1000000&& (P2=wbuf,ws=-1,fwrite (wbuf,1,1000001,stdout)), ++ws,*p2++=x;} Il void puts (const char str[]) {fwrite (wbuf,1,ws+1,stdout)? (       Ws=-1): 0,fwrite (Str,1,strlen (str), stdout);}       Il void gl (string& s) {for (res char ch; (CH=GC ())! = ' \ n ' &&fok;) s+=ch;} Il io& operator>> (int& x) {x=0;res char f=0,ch=gc (), while (Dsep&&fok) f|= (ch== '-'), CH=GC (); (IsDigit (CH)) x= (x<<1) + (x< <3) + (ch^48), CH=GC (); return x=f?-x:x,*this;} Il io& operator>> (ll& x) {x=0;res char f=0,ch=gc (), while (Dsep&&fok) f|= (ch== '-'), CH=GC ();       IsDigit (CH)) x= (x<<1) + (x<<3) + (ch^48), CH=GC (); return x=f?-x:x,*this;}       Il io& operator>> (char& ch) {return CH=GC (), *this;} Il io& operator>> (string& s) {res char CH=GC (), while (Sep&&fok) CH=GC (), while (!sep&&fok)       S+=CH,CH=GC (); return *this;} Il io& operator>> (double& x) {x=0;res char f=0,ch=gc ();d ouble d=0.1;while (Dsep&&fok) f|= (ch== '-' ), CH=GC (), while (IsDigit (CH)) x=x*10+ (ch^48), CH=GC (); if (ch== '. ')       while (IsDigit (CH=GC ())) x+=d* (ch^48), D*=0.1;return x=f?-x:x,*this;} Il io& operator<< (int x) {res char ch[10],i=-1;! X? (PC (' 0 '), 0): 0,x<0?       (PC ('-'), x=-x): 0;while (x) ch[++i]=x%10+48,x/=10;while (~i) PC (Ch[i]),--I;return *this;} Il io& operator<< (ll x) {res char ch[20],i=-1;! X? (PC (' 0 '), 0): 0,x<0? (PC ('-'), x=-x): 0;while (x) ch[++i]=x%10+48,x/=10;while (~i) PC (Ch[i]),--I;return *this;}       Il io& operator<< (char ch) {return PC (CH), *this;}       Il io& operator<< (char str[]) {return puts (str), *this;} Il io& operator<< (double x) {int y=int (x); *this<<y;x-=y;while (NEQ (X,int (x))) x*=10;x?*this<< '. '       <<int (x): 0;return *this;} Il operator bool () {return b;}} io; #define N 1001int n,m,s,cnt,cnt,d[n],d[n],head[n],head[n];bool v[n];struct edge{int to,w,nxt;} E[100001],E[100001]; #define FL (i,x) for (ri i=head[x],to;to=e[i].to,i;i=e[i].nxt) struct cmp{bool operator () (int a,int b) {return d[a]>d[b];}}; Priority_queue<int,vector<int>,cmp>q;il void Add (int x,int y,int W) {E[++CNT].TO=Y;E[CNT].W=W;E[CNT].NXT =head[x];head[x]=cnt;} Il void ADD (int x,int y,int W) {e[++cnt].to=y; E[cnt].w=w; E[CNT].NXT=HEAD[X]; head[x]=cnt;}    Il void Spfa () {clr (d,126); CLR (d,126);    D[s]=d[s]=0;q.push (s);    int x;        while (!q.empty ()) {v[x=q.top ()]=0;q.pop ();   FL (i,x)     if (D[x]+e[i].w<d[to]) {D[TO]=D[X]+E[I].W;        if (!v[to]) Q.push (to), v[to]=1;            } FL (I,x) if (D[x]+e[i].w<d[to]) {D[TO]=D[X]+E[I].W;        if (!v[to]) Q.push (to), v[to]=1;    }}}int Main () {io>>n>>m>>s;    int x,y,w,ans=0;    Fur (i,1,m) Io>>x>>y>>w,add (x,y,w), add (Y,X,W);    SPFA ();    Fur (i,1,n) Ans=max (Ans,d[i]+d[i]); io<<ans<< ' \ n ';}

Eggs:

Double experience: Luogu P1629 postman Messenger

(change all the maximum values to all the sums.)

luogu-judger-enable-o2#include<bits/stdc++.h> #pragma GCC optimize (3) namespace zdy{#define RES Register #de Fine ri Res int #define LL Long long #define DB double #define SHT short #define IL inline #define MB Templ Ate <class t> #define FUR (i,x,y) for (RI i=x;i<=y;i++) #define FUR (I,x,y) for (i=x;i<=y;i++) #define Fd R (i,x,y) for (RI i=x;i>=y;i--) #define IN2 (x, Y) in (×), in (#define) #define IN3 (x, z) in2 (z) in4 (a,b,c , d) in2 (A, B), in2 (c,d) #define OUTN (x) out (x), PC (' \ n ') #define CLR (x, y) memset (x,y,sizeof (×)) #define CPY (y) mem CPY (x,y,sizeof (x)) #define FL (i,x) for (RI i=head[x],to;to=e[i].to,i;i=e[i].nxt) #define INF 2147483630 #define FI N (s) freopen (S ".", "R", stdin) #define FOUT (s) freopen (S ". Out", "w", stdin) #define GT IO.GC () #define L2 (N) (log (n    )/log (2)) MB il T ABS (t x) {return x>0?x:-x;}    MB il t MAX (t x,t y) {return x>y?x:y;}    MB il t MIN (t x,t y) {return x<y?x:y;} MB IL T GCD (t x,t y) {return y?    GCD (y,x%y): x;} MB il void SWAP (t x,t y) {T t=x;y=t;x=y;}} Using namespace zdy;using namespace Std;class io{#define FOK (ch!=eof) #define SEP (ch== "| | ch== ' \ n ' | | ch== ' \ t ') #define DSEP!isdigit (CH) #define NEQ (A, a) ((a)-(b) >1e-6) Char Rbuf[1<<20],wbuf[1<<20],b,*p   1,*P2;   int rs,ws,s;       Public:io ():p 1 (rbuf), p2 (wbuf), S (1000000), RS (1000000), WS ( -1), B (1) {} ~io () {fwrite (wbuf,1,ws+1,stdout);} Il char GC () {return rs==s&& (P1=rbuf,rs=-1, (S=fread (Rbuf,1,s+1,stdin)-1) ==-1)? (       b=0,eof):(++rs,*p1++);}       Il void pc (int x) {ws==1000000&& (P2=wbuf,ws=-1,fwrite (wbuf,1,1000001,stdout)), ++ws,*p2++=x;} Il void puts (const char str[]) {fwrite (wbuf,1,ws+1,stdout)? (       Ws=-1): 0,fwrite (Str,1,strlen (str), stdout);}       Il void gl (string& s) {for (res char ch; (CH=GC ())! = ' \ n ' &&fok;) s+=ch;} Il io& operator>> (int& x) {x=0;res char f=0,ch=gc (), while (Dsep&&fok) f|= (ch== '-'), CH=GC (); (IsDigit(CH))       x= (x<<1) + (x<<3) + (ch^48), CH=GC (); return x=f?-x:x,*this;} Il io& operator>> (ll& x) {x=0;res char f=0,ch=gc (), while (Dsep&&fok) f|= (ch== '-'), CH=GC ();       IsDigit (CH)) x= (x<<1) + (x<<3) + (ch^48), CH=GC (); return x=f?-x:x,*this;}       Il io& operator>> (char& ch) {return CH=GC (), *this;} Il io& operator>> (string& s) {res char CH=GC (), while (Sep&&fok) CH=GC (), while (!sep&&fok)       S+=CH,CH=GC (); return *this;} Il io& operator>> (double& x) {x=0;res char f=0,ch=gc ();d ouble d=0.1;while (Dsep&&fok) f|= (ch== '-' ), CH=GC (), while (IsDigit (CH)) x=x*10+ (ch^48), CH=GC (); if (ch== '. ')       while (IsDigit (CH=GC ())) x+=d* (ch^48), D*=0.1;return x=f?-x:x,*this;} Il io& operator<< (int x) {res char ch[10],i=-1;! X? (PC (' 0 '), 0): 0,x<0?       (PC ('-'), x=-x): 0;while (x) ch[++i]=x%10+48,x/=10;while (~i) PC (Ch[i]),--I;return *this;} Il io& operator<< (ll x) {res char ch[20],i=-1;! X? (PC (' 0 '), 0):0,x<0?       (PC ('-'), x=-x): 0;while (x) ch[++i]=x%10+48,x/=10;while (~i) PC (Ch[i]),--I;return *this;}       Il io& operator<< (char ch) {return PC (CH), *this;}       Il io& operator<< (char str[]) {return puts (str), *this;} Il io& operator<< (double x) {int y=int (x); *this<<y;x-=y;while (NEQ (X,int (x))) x*=10;x?*this<< '. '       <<int (x): 0;return *this;} Il operator bool () {return b;}} io; #define N 1001int n,m,cnt,cnt,d[n],d[n],head[n],head[n];bool v[n];struct edge{int to,w,nxt;} E[100001],E[100001]; #define FL (i,x) for (ri i=head[x],to;to=e[i].to,i;i=e[i].nxt) struct cmp{bool operator () (int a,int b) {return d[a]>d[b];}}; Priority_queue<int,vector<int>,cmp>q;il void Add (int x,int y,int W) {E[++CNT].TO=Y;E[CNT].W=W;E[CNT].NXT =head[x];head[x]=cnt;} Il void ADD (int x,int y,int W) {e[++cnt].to=y; E[cnt].w=w; E[CNT].NXT=HEAD[X]; head[x]=cnt;}    Il void Spfa () {clr (d,126); CLR (d,126);    D[1]=d[1]=0;q.push (1);    int x; while (!q.empty ()) {v[x=q.top ()]=0;Q.POP ();            FL (i,x) if (D[x]+e[i].w<d[to]) {D[TO]=D[X]+E[I].W;        if (!v[to]) Q.push (to), v[to]=1;            } FL (I,x) if (D[x]+e[i].w<d[to]) {D[TO]=D[X]+E[I].W;        if (!v[to]) Q.push (to), v[to]=1;    }}}int Main () {io>>n>>m;    int x,y,w,ans=0;    Fur (i,1,m) Io>>x>>y>>w,add (x,y,w), add (Y,X,W);    SPFA ();    Fur (I,2,n) ans+=d[i]+d[i]; io<<ans<< ' \ n ';}

[Usaco07feb] Silver Bull Party Cow Parties