[AtCoder] E - Edge Deletion

E - Edge Deletion

  • Time : O(v^3 + ve)
  • Space : O(n^2)
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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")//Comment optimisations for interactive problems (use endl)
#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 MAX_N 101010
#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(ll n, vall3& E) {
vvll dis(n + 1, vll(n + 1, 1e18));
for(auto& [u, v, w] : E) {
dis[u][v] = dis[v][u] = min(dis[u][v], w);
}
for(ll k = 1; k <= n; k++) {
for(ll i = 1; i <= n; i++) {
for(ll j = 1; j <= n; j++) {
dis[i][j] = min(dis[i][j], dis[i][k] + dis[k][j]);
}
}
}
ll res = 0;
for(auto& [u, v, w] : E) {
bool use = true;
for(ll i = 1; i <= n and use; i++) {
if(dis[u][i] + dis[i][v] <= w)
use = false;
}
if(!use) res++;
}
return res;
}

int main() {
ios_base::sync_with_stdio(0);
ios::sync_with_stdio(0);
cin.tie(0);
ll tc = 1;
//cin>>tc;
for(ll i = 1; i <= tc; i++) {
ll n, m;
cin>>n>>m;
vall3 E(m);
for(ll j = 0; j < m; j++) cin>>E[j][0]>>E[j][1]>>E[j][2];
cout<<solve(n,E)<<endl;
}
return 0;
}
Author: Song Hayoung
Link: https://songhayoung.github.io/2022/06/20/PS/AtCoder/abc243-e/
Copyright Notice: All articles in this blog are licensed under CC BY-NC-SA 4.0 unless stating additionally.