求助dij+二分
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求助dij+二分
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black__ice楼主2022/5/19 14:04
#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>
#include <limits.h>
#include <vector>
using namespace std;

const int N = 1e5+10;
typedef pair<int,int> PII;
typedef long long ll;
int h[N],w[N],e[N],ne[N],idx;
ll d[N],f[N];
bool st[N];
int n,m,b;

void add(int a,int b,int c)
{
	e[idx] = b,w[idx] = c,ne[idx] = h[a],h[a] = idx++;
}

bool check(ll k)
{
	if(f[1] > k || f[n] > k) return false;
	for(int i = 0;i <= n;i++)
	{
		d[i] = INT_MAX;
		st[i] = false;
	}
	priority_queue<PII,vector<PII>,greater<PII>> heap;
	d[1] = 0;
	heap.push({0,1});

	while(heap.size())
	{
		auto t = heap.top();
		heap.pop();
		int ver = t.second,blood = t.first;
		if(st[ver]) continue;
		st[ver] = true;
		for(int i = h[ver];i != -1;i = ne[i])
		{
			int j = e[i];
			if(d[j] > blood + w[i] && f[j] <= k)
			{
				d[j] = blood + w[i];
				if(!st[j]) heap.push({d[j],j});
			}
		}
	}
	return (d[n] <= b);
}

int main()
{
	memset(h,-1,sizeof h);
	cin >> n >> m >> b;
	long long l = 1e9 + 10,r = -1;
	for(int i = 1;i <= n;i++) 
	{
		scanf("%lld",&f[i]);
		r = max(r,f[i]);
	}
	l = max(f[1],f[n]);
	for(int i = 0;i < m;i++)
	{
		int a,b,w;
		scanf("%d%d%d",&a,&b,&w);
		if(a==b) continue;
		add(a,b,w),add(b,a,w);
	}
	while(l < r)
	{
		long long mid = (l + r) >> 1;
		if(check(mid)) r = mid;
		else l = mid + 1;
	}
	if(!check(l)) puts("AFK");
	else cout << l  << endl;
}

2022/5/19 14:04
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