Submission #31939

#	Time	Username	Problem	Language	Result	Execution time	Memory
31939		minchurl	Beads and wires (APIO14_beads)	C++11	0 / 100	6 ms	4992 KiB

beads

#include<stdio.h>
#include<math.h>
#include<vector>
#define LL long long
#define MAX_N 200005
#define MAX(x,y) ((x)>(y)?(x):(y))
using namespace std;
struct emp{
	LL y,cost;
	bool operator < (emp d) const{
		return cost>d.cost;
	}
};
LL n;
LL master[MAX_N],branch[MAX_N];
vector<emp> net[MAX_N];
void make_branch(LL x,LL pa,LL cost){
	LL i,sz;
	sz=net[x].size();
	branch[pa]=MAX(branch[pa],branch[x]);
	for(i=0;i<sz;i++){
		if(net[x][i].y==pa)	continue;
		branch[pa]=MAX(branch[pa],branch[net[x][i].y]+net[x][i].cost+cost);
	}
}
void merge(LL x,LL pa,LL cost){
	LL i,sum,sz;
	emp max_branch[3],max_master[3];
	max_branch[0].cost=max_branch[1].cost=-1;
	max_branch[0].y=max_branch[1].y=0;
	max_master[0].cost=max_master[1].cost=-1;
	max_master[0].y=max_master[1].y=0;
	sz=net[x].size();
	if(pa && sz<3)	return;
	if(!pa && sz<2)	return;
	for(i=0;i<sz;i++){
		if(net[x][i].y==pa)	continue;
		if(branch[net[x][i].y]+net[x][i].cost>max_branch[0].cost){
			max_branch[1]=max_branch[0];
			max_branch[0].cost=branch[net[x][i].y]+net[x][i].cost;
			max_branch[0].y=net[x][i].y;
		}else if(branch[net[x][i].y]+net[x][i].cost>max_branch[1].cost){
			max_branch[1].cost=branch[net[x][i].y]+net[x][i].cost;
			max_branch[1].y=net[x][i].y;
		}
	}
	for(i=0;i<sz;i++){
		if(net[x][i].y==pa)	continue;
		if(master[net[x][i].y]+net[x][i].cost>max_master[0].cost){
			max_master[1]=max_master[0];
			max_master[0].cost=master[net[x][i].y]+net[x][i].cost;
			max_master[0].y=net[x][i].y;
		}else if(master[net[x][i].y]+net[x][i].cost>max_master[1].cost){
			max_master[1].cost=master[net[x][i].y]+net[x][i].cost;
			max_master[1].y=net[x][i].y;
		}
	}
	if(max_master[0].y-max_branch[0].y){

		master[x]=MAX(master[x],max_master[0].cost+max_branch[0].cost);
	}else{
		master[x]=MAX(master[x],MAX(max_master[0].cost+max_branch[1].cost,max_master[1].cost+max_branch[0].cost));
	}
}
void make_master(LL x,LL pa,LL cost){
	LL i,sz;
	sz=net[x].size();
	for(i=0;i<sz;i++){
		if(net[x][i].y-pa)	make_master(net[x][i].y,x,net[x][i].cost);
		master[x]=MAX(master[x],master[net[x][i].y]);
	}
	make_branch(x,pa,cost);
	merge(x,pa,cost);

}
int main(){
	LL i,x,y,cost;
	emp node;
	scanf("%lld",&n);
	for(i=1;i<n;i++){
		scanf("%lld %lld %lld",&x,&y,&cost);
		node.y=y;
		node.cost=cost;
		net[x].push_back(node);
		node.y=x;
		net[y].push_back(node);
	}
	make_master(1,0,0);
	printf("%lld\n",master[1]);
	return 0;
}

Compilation message (stderr)

beads.cpp: In function 'void merge(long long int, long long int, long long int)':
beads.cpp:27:7: warning: unused variable 'sum' [-Wunused-variable]
  LL i,sum,sz;
       ^~~
beads.cpp: In function 'int main()':
beads.cpp:79:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld",&n);
  ~~~~~^~~~~~~~~~~
beads.cpp:81:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lld %lld %lld",&x,&y,&cost);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 13
• Subtask 2: 0 / 15
• Subtask 3: 0 / 29
• Subtask 4: 0 / 43