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| #include <bits/stdc++.h>
#pragma optimization_level 3
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math,O3")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx")
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization ("unroll-loops")
struct PairHash {
inline std::size_t operator()(const std::pair<int, int> &v) const { return v.first * 31 + v.second; }
};
#define M_PI 3.14159265358979323846
#define MAX_N 202020
#define INF 987654321
#define EPS 1e-9
#define ll long long
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vall3 vector<array<ll,3>>
#define all3 array<ll,3>
#define all5 array<ll,5>
#define vall5 vector<all5>
#define vll vector<ll>
#define vi vector<int>
#define vs vector<string>
#define usll unordered_set<ll>
#define uspll unordered_set<pll, PairHash>
#define umll unordered_map<ll,ll>
#define vvs vector<vs>
#define vvll vector<vll>
#define all(a) begin(a), end(a)
#define rall(a) rbegin(a), rend(a)
ll __gcd(ll x, ll y) { return !y ? x : __gcd(y, x % y); }
using namespace std;
ll solve(vll H, vpll E) {
ll res = 0, n = H.size();
vector<vpll> adj(n);
for(auto& [u, v] : E) {
adj[u].push_back({v,max(0ll, H[v] - H[u])});
adj[v].push_back({u, max(0ll, H[u] - H[v])});
}
vll vis(n, 1e12);
priority_queue<pll> pq;
pq.push({0, 1});
vis[1] = 0;
while(!pq.empty()) {
auto [w, u] = pq.top(); pq.pop();
if(vis[u] != -w) continue;
res = max(res, H[1] - H[u] - vis[u]);
for(auto& [v, w] : adj[u]) {
if(vis[u] + w < vis[v]) {
vis[v] = vis[u] + w;
pq.push({-vis[v], v});
}
}
}
return res;
}
int main() {
ios_base::sync_with_stdio(0);
ios::sync_with_stdio(0);
cin.tie(0);
cout.precision(12);
ll tc = 1;
for (ll i = 1; i <= tc; i++) {
ll v, e;
cin>>v>>e;
vpll E(e);
vll H(v + 1);
for(ll j = 1; j <= v; j++) cin>>H[j];
for(ll j = 0; j < e; j++) cin>>E[j].first>>E[j].second;
cout<<solve(H, E)<<endl;
}
return 0;
}
|
