传送门
Version 1: Dijkstra
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const ll _inf(0x3f3f3f3f3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(1e5 + 10);
const int maxm(2e5 + 10);
int ecnt, head[maxn];
ll dis[maxn];
bool vis[maxn];
struct edge {
int to, wt, nxt;
} edges[maxm];
template<typename T = int>
inline const T read()
{
T x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = (x << 3) + (x << 1) + ch - '0';
ch = getchar();
}
return x * f;
}
template<typename T>
inline void write(T x, char c)
{
if (x < 0) {
putchar('-');
x = -x;
}
if (x > 9) write(x / 10, false);
putchar(x % 10 + '0');
if (c) putchar(c);
}
void addEdge(int u, int v, int w)
{
edges[ecnt].to = v;
edges[ecnt].wt = w;
edges[ecnt].nxt = head[u];
head[u] = ecnt++;
}
void dijkstra(int src)
{
priority_queue<p, vector<p>, greater<p>> q;
q.push(p(0, src));
dis[src] = 0;
while (not q.empty()) {
int u = q.top().second;
q.pop();
if (vis[u]) continue;
vis[u] = true;
for (int i = head[u]; ~i; i = edges[i].nxt) {
int v = edges[i].to, w = edges[i].wt;
if (dis[v] > dis[u] + w) {
dis[v] = dis[u] + w;
q.push(p(dis[v], v));
}
}
}
}
int main()
{
#ifdef ONLINE_JUDGE
#else
freopen("input.txt", "r", stdin);
#endif
memset(head, -1, sizeof head);
memset(dis, 0x3f, sizeof dis);
int n = read(), m = read(), s = read();
while (m--) {
int u = read(), v = read(), w = read();
addEdge(u, v, w);
}
dijkstra(s);
for (int i = 1; i <= n; ++i) {
write(dis[i] == _inf ? INT_MAX : dis[i], i == n ? '
' : ' ');
}
return 0;
}
Version 2: SPFA
SPFA 已死
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const ll _inf(0x3f3f3f3f3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(1e5 + 10);
const int maxm(2e5 + 10);
int ecnt, head[maxn];
ll dis[maxn];
bool vis[maxn];
struct edge {
int to, wt, nxt;
} edges[maxm];
template<typename T = int>
inline const T read()
{
T x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = (x << 3) + (x << 1) + ch - '0';
ch = getchar();
}
return x * f;
}
template<typename T>
inline void write(T x, char c)
{
if (x < 0) {
putchar('-');
x = -x;
}
if (x > 9) write(x / 10, false);
putchar(x % 10 + '0');
if (c) putchar(c);
}
void addEdge(int u, int v, int w)
{
edges[ecnt].to = v;
edges[ecnt].wt = w;
edges[ecnt].nxt = head[u];
head[u] = ecnt++;
}
void spfa(int src)
{
queue<int> q;
q.push(src);
dis[src] = 0;
vis[src] = true;
while (not q.empty()) {
int u = q.front();
q.pop();
vis[u] = false;
for (int i = head[u]; ~i; i = edges[i].nxt) {
int v = edges[i].to, w = edges[i].wt;
if (dis[v] > dis[u] + w) {
dis[v] = dis[u] + w;
if (not vis[v]) {
q.push(v);
vis[v] = true;
}
}
}
}
}
int main()
{
#ifdef ONLINE_JUDGE
#else
freopen("input.txt", "r", stdin);
#endif
memset(head, -1, sizeof head);
memset(dis, 0x3f, sizeof dis);
int n = read(), m = read(), s = read();
while (m--) {
int u = read(), v = read(), w = read();
addEdge(u, v, w);
}
spfa(s);
for (int i = 1; i <= n; ++i) {
write(dis[i] == _inf ? INT_MAX : dis[i], i == n ? '
' : ' ');
}
return 0;
}
Version 3 SPFA Swap-SLF 优化
SPFA 玄学优化 https://www.luogu.com.cn/blog/xhhkwy/spfa-hacker-orzorz
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using p = pair<int, int>;
const double pi(acos(-1));
const int inf(0x3f3f3f3f);
const int mod(1e9 + 7);
const int maxn(1e5 + 10);
const int maxm(1e6 + 10);
int ecnt, head[maxn];
int dis[maxn];
bool vis[maxn];
deque<int> q;
struct edge {
int to, wt, nxt;
} edges[maxm];
template<typename T = int>
inline const T read()
{
T x = 0, f = 1;
char ch = getchar();
while (ch < '0' || ch > '9') {
if (ch == '-') f = -1;
ch = getchar();
}
while (ch >= '0' && ch <= '9') {
x = (x << 3) + (x << 1) + ch - '0';
ch = getchar();
}
return x * f;
}
template<typename T>
inline void write(T x, char c)
{
if (x < 0) {
putchar('-');
x = -x;
}
if (x > 9) write(x / 10, false);
putchar(x % 10 + '0');
if (c) putchar(c);
}
void addEdge(int u, int v, int w)
{
edges[ecnt].to = v;
edges[ecnt].wt = w;
edges[ecnt].nxt = head[u];
head[u] = ecnt++;
}
void swap_slf()
{
if (q.size() > 2 and dis[q.front()] > dis[q.back()]) {
swap(q.front(), q.back());
}
}
void spfa(int src)
{
dis[src] = 0;
q.push_back(src);
vis[src] = true;
while (not q.empty()) {
int u = q.front();
q.pop_front();
swap_slf();
vis[u] = false;
for (int i = head[u]; compl i; i = edges[i].nxt) {
int v = edges[i].to, w = edges[i].wt;
if (dis[v] > dis[u] + w) {
dis[v] = dis[u] + w;
if (not vis[v]) {
q.push_back(v);
swap_slf();
vis[v] = true;
}
}
}
}
}
int main()
{
#ifdef ONLINE_JUDGE
#else
freopen("input.txt", "r", stdin);
#endif
memset(head, -1, sizeof head);
memset(dis, 0x3f, sizeof dis);
int n = read(), m = read(), s = read();
while (m--) {
int u = read(), v = read(), w = read();
addEdge(u, v, w);
}
spfa(s);
for (int i = 1; i <= n; ++i) {
if (dis[i] == inf) {
puts("NO PATH");
} else {
write(dis[i], i == n ? 10 : 32);
}
}
return 0;
}