SPFA (lib/graph/spfa.hpp)

• View this file on GitHub
• Last update: 2025-06-10 13:57:57+09:00
• Include: #include "lib/graph/spfa.hpp"
• Link: https://ei1333.github.io/luzhiled/snippets/graph/shortest-path-faster-algorithm.html
• Link: https://hogloid.hatenablog.com/entry/20120409/1333973448

Depends on

• 重み付きグラフ (lib/graph/graph.hpp)

Verified with

• test/aoj/grl/spfa.test.cpp

Code

#pragma once
#include <limits>
#include <queue>
#include <vector>
#include "graph/graph.hpp"

/// @brief SPFA
/// @see https://hogloid.hatenablog.com/entry/20120409/1333973448
/// @see https://ei1333.github.io/luzhiled/snippets/graph/shortest-path-faster-algorithm.html
template <class T>
std::vector<T> shortest_path_faster_algorithm(Graph<T> &g, int s, T inf = std::numeric_limits<T>::max()) {
    int n = g.size();
    std::vector<T> dists(n, inf);
    std::vector<int> pending(n, 0), times(n, 0);
    std::queue<int> que;
    que.emplace(s);
    pending[s] = true;
    ++times[s];
    dists[s] = 0;
    while (!que.empty()) {
        int p = que.front();
        que.pop();
        pending[p] = false;
        for (auto &e : g[p]) {
            if (!(dists[p] + e.weight() < dists[e.to()])) continue;
            dists[e.to()] = dists[p] + e.weight();
            if (!pending[e.to()]) {
                if (++times[e.to()] >= n) return std::vector<T>();
                pending[e.to()] = true;
                que.emplace(e.to());
            }
        }
    }
    return dists;
}

Traceback (most recent call last):
  File "/home/runner/.local/lib/python3.12/site-packages/competitive_verifier/oj/resolver.py", line 291, in resolve
    bundled_code = language.bundle(path, basedir=basedir)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/runner/.local/lib/python3.12/site-packages/competitive_verifier/oj/verify/languages/cplusplus.py", line 242, in bundle
    bundler.update(path)
  File "/home/runner/.local/lib/python3.12/site-packages/competitive_verifier/oj/verify/languages/cplusplus_bundle.py", line 479, in update
    self._resolve(pathlib.Path(included), included_from=path)
  File "/home/runner/.local/lib/python3.12/site-packages/competitive_verifier/oj/verify/languages/cplusplus_bundle.py", line 286, in _resolve
    raise BundleErrorAt(path, -1, "no such header")
competitive_verifier.oj.verify.languages.cplusplus_bundle.BundleErrorAt: graph/graph.hpp: line -1: no such header

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