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Markdown Test

MD Test:

MD Test:

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Inline Code: int main() { printf("Hello World!\n"); //Hello world }

Reference: suncongbo Codeforces Round 250 (Div. 1) 530A - Quadratic equation

using namespace std;

const int N = 2e5;
const int C = 1e6;
const int INF = 1e8;
struct Edge {int nxt,v,w;} e[(N<<1)+2];
int tmp[N+2];
int t[C+2];
int dis[N+2];
int dep[N+2];
int fe[N+2];
int sz[N+2];
int cur[N+2];
bool vis[N+2];
int n,m,mn,c,rt,siz,ans,tp;

void addedge(int u,int v,int w)
{
    m++; e[m].v = v; e[m].w = w;
    e[m].nxt = fe[u]; fe[u] = m;
}

void getroot(int u,int prv)
{
    sz[u] = 1; cur[u] = 0;
    for(int i=fe[u]; i; i=e[i].nxt)
    {
        if(e[i].v==prv || vis[e[i].v]==true) continue;
        getroot(e[i].v,u);
        sz[u] += sz[e[i].v]; cur[u] = max(cur[u],sz[e[i].v]);
    }
    cur[u] = max(cur[u],siz-sz[u]);
    if(cur[u]<mn) {mn = cur[u]; rt = u;}
}

void dfs(int u,int prv)
{
	tp++; tmp[tp] = u;
	for(int i=fe[u]; i; i=e[i].nxt)
	{
		if(vis[e[i].v]==true || e[i].v==prv) continue;
		dep[e[i].v] = dep[u]+1; dis[e[i].v] = dis[u]+e[i].w;
		if(dis[e[i].v]>c) dis[e[i].v] = c+1;
		dfs(e[i].v,u);
	}
}

void pdc(int u)
{
	vis[u] = true;
    tp = 0;
	for(int i=fe[u]; i; i=e[i].nxt)
	{
		if(vis[e[i].v]==true) continue;
		dis[e[i].v] = e[i].w; dep[e[i].v] = 1; 
		dfs(e[i].v,u);
		for(int j=1; j<=tp; j++) {if(dis[tmp[j]]<c) ans = min(ans,t[c-dis[tmp[j]]]+dep[tmp[j]]);}
		for(int j=1; j<=tp; j++) {if(dis[tmp[j]]<=c) t[dis[tmp[j]]] = min(t[dis[tmp[j]]],dep[tmp[j]]);}
		ans = min(ans,t[c]);
	}
	for(int i=1; i<=tp; i++) {if(dis[tmp[i]]<=c) t[dis[tmp[i]]] = INF;}
	for(int i=fe[u]; i; i=e[i].nxt)
	{
		if(vis[e[i].v]==true) continue;
		rt = 0; mn = INF; siz = sz[e[i].v];
		getroot(e[i].v,0); pdc(rt);
	}
}

int main()
{
    scanf("%d%d",&n,&c); m = 0;
    if(c==0) {puts("0"); return 0;}
    for(int i=1; i<n; i++)
    {
        int x,y,z; scanf("%d%d%d",&x,&y,&z); x++; y++;
        if(z>c) z = c+1;
        addedge(x,y,z); addedge(y,x,z);
    }
    for(int i=1; i<=c; i++) t[i] = INF;
    siz = sz[1] = n; rt = 0; ans = INF; mn = INF;
    getroot(1,0); pdc(rt);
    printf("%d\n",ans==INF ? -1 : ans);
    return 0;
}