Problem Link : http://www.lightoj.com/volume_showproblem.php?problem=1257
/* +-+ +-+ +-+ |R| |.| |S| +-+ +-+ +-+ */ #include <bits/stdc++.h> #define pii pair <int,int> #define sc scanf #define pf printf #define Pi 2*acos(0.0) #define ms(a,b) memset(a, b, sizeof(a)) #define pb(a) push_back(a) #define MP make_pair #define db double #define ll long long #define EPS 10E-10 #define ff first #define ss second #define sqr(x) (x)*(x) #define D(x) cout<<#x " = "<<(x)<<endl #define VI vector <int> #define DBG pf("Hi\n") #define MOD 100007 #define MAX 30001 #define CIN ios_base::sync_with_stdio(0); cin.tie(0) #define SZ(a) (int)a.size() #define sf(a) scanf("%d",&a) #define sff(a,b) scanf("%d%d",&a,&b) #define sfff(a,b,c) scanf("%d%d%d",&a,&b,&c) #define loop(i,n) for(int i=0;i<n;i++) #define REP(i,a,b) for(int i=a;i<b;i++) #define TEST_CASE(t) for(int z=1;z<=t;z++) #define PRINT_CASE printf("Case %d:\n",z) #define all(a) a.begin(),a.end() #define intlim 2147483648 #define inf 1000000 #define ull unsigned long long using namespace std; vector<int> graph[MAX],cost[MAX]; int dis[MAX]; int dis1[MAX]; int a,b,max_dis,n; void BFS(int src) { dis[src]=0; queue<int>Q; Q.push(src); while(!Q.empty()) { int u= Q.front(); Q.pop(); if(dis[u]>max_dis) { max_dis=dis[u]; a=u; } loop(i,SZ(graph[u])) { int v=graph[u][i]; if(dis[v]==-1) { dis[v]=dis[u]+cost[u][i]; Q.push(v); } } } } void BFS1(int src) { dis1[src]=0; queue<int>Q; Q.push(src); while(!Q.empty()) { int u= Q.front(); Q.pop(); loop(i,SZ(graph[u])) { int v=graph[u][i]; if(dis1[v]==-1) { dis1[v]=dis1[u]+cost[u][i]; Q.push(v); } } } } void allclear() { loop(i,n+1) { graph[i].clear(); cost[i].clear(); dis[i]=-1; dis1[i]=-1; } max_dis=-1; a=b=-1; } int main() { ///freopen("in.txt","r",stdin); ///freopen("out.txt","w",stdout); int t,x,y,w; sf(t); TEST_CASE(t) { sf(n); allclear(); loop(i,n-1) { sfff(x,y,w); graph[x].pb(y); graph[y].pb(x); cost[x].pb(w); cost[y].pb(w); } BFS(0); b=a; loop(i,n+1) dis[i]=-1; max_dis=-1; BFS(b); b=a; BFS1(b); PRINT_CASE; loop(i,n) { pf("%d\n",max(dis[i],dis1[i])); } } return 0; }
Algorithm:
1. Run a BFS from any node and determine the farthest node from it and Name this node as b.
2. Run another BFS from b and save all node’s distance from b (dis array). and determine the farthest node from b and name this node as a;
3. Run another BFS from a and save all nodes distance from a (dis1 array).
4. Now print for all node max(dis[node], dis1[node]).