提出 #2095014

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ソースコード 拡げる

#include<bits/stdc++.h>

using namespace std;
using ll = long long;
using ld = long double;
#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define reps(i,s,n) for(int i=(int)(s);i<(int)(n);i++)
#define all(c) begin(c),end(c)
const ll INF = ll(1e16);
const ll mod = ll(1e9 + 7);

const int MAX_E = 2000;
const int MAX_V = 1000;

struct edge { int from, to; ll cost; };

edge es[MAX_E];

ll d[MAX_V];
int V, E;

//s番目の頂点から各頂点への最短距離
void bellman_ford(int s) {
	for (int i = 0; i < V; i++)d[i] = INF;
	d[s] = 0;
	while (1) {
		bool update = false;
		for (int i = 0; i < E; i++) {
			edge e = es[i];
			if (d[e.from] != INF&&d[e.to] > d[e.from] + e.cost) {
				d[e.to] = d[e.from] + e.cost;
				update = true;
			}
		}
		if (!update)break;
	}
}

bool find_negative_loop() {
	memset(d, 0, sizeof(d));
	for (int i = 0; i < V; i++) {
		for (int j = 0; j < E; j++) {
			edge e = es[j];
			if (d[e.to] > d[e.from] + e.cost) {
				d[e.to] = d[e.from] + e.cost;
				if (i == V - 1)return true;
			}
		}
	}
	return false;
}

int main() {
	cin >> V >> E;
	rep(i, E) {
		int a, b, c;
		cin>>a>>b>>c;
		es[i].from = --a; es[i].to = --b; es[i].cost = -c;
	}
	if (find_negative_loop())cout << "inf" << endl;
	else {
		bellman_ford(0);
		cout << -d[V-1] << endl;
	}
	return 0;
}

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