无环最长简单路径

标题有点累赘，好像无环就可以保证绝对简单了，下面给出代码的实现

LongestPath.h

#pragma once

#include <stack>
#include <list>
#include <cstring>
#include <iostream>

class adjNode
{
    int v, weight;

public:
    adjNode(int v, int weight) :v(v), weight(weight){}
    adjNode() = default;
    //adjNode(adjNode&&) = default;
    int getV() { return v; }
    int getWeight(){ return weight; }
};

class graph
{
    int node_sum;
    //记得加std
    std::list<adjNode> **adj;

    void topoSort(int s, bool visited[], std::stack<int> &Stack);

public:
    graph(int v);
    ~graph() { 
        for (int i = 0;i < node_sum;i++)
            delete adj[i];
        delete adj; 
    }
    void addEdge(int u, int v, int w);
    void longestPath(int s);//源节点到各点距离以打印方式呈现，或者可以返回一个vector

};
void graph::topoSort(int s, bool visited[], std::stack<int> &Stack)
{
    visited[s] = 0;

    for (auto it = adj[s]->begin();it != adj[s]->end();++it)
    {
        if (!visited[it->getV()])
            topoSort(it->getV(), visited, Stack);
    }
    Stack.push(s);
}

void graph::addEdge(int u, int v, int weight)
{
    adj[u]->push_back(adjNode(v, weight));
}

graph::graph(int v) :node_sum(v)
{
    adj = new std::list<adjNode>* [node_sum];
    for (int i = 0;i < node_sum;i++)
        adj[i] = new std::list <adjNode>();
}

void graph::longestPath(int s)
{
    std::stack<int> sta;
    int *dist = new int[node_sum];
    bool *visited = new bool[node_sum];

    memset(visited, 0, sizeof(visited));
    for (int i = 0;i < node_sum;i++)
        dist[i] = INT_MIN;
    //memset(dist, -1, sizeof(dist));
    dist[s] = 0;

    for (int i = 0;i < node_sum;i++)
        if (!visited[i])
            topoSort(i, visited, sta);

    while (!sta.empty()) {
        int u = sta.top();
        sta.pop();

        if (dist[u] != INT_MIN)
            for (auto it = adj[u]->begin();it != adj[u]->end();++it)
                if (dist[it->getV()] < dist[u] + it->getWeight())
                    dist[it->getV()] = dist[u] + it->getWeight();
    }
    for (int i = 0;i < node_sum;i++)std::cout << dist[i] << " ";
    std::cout << std::endl;

    delete visited;
    delete dist;
}

这是借鉴某博客的，后面追根溯源找到了https://www.geeksforgeeks.org/find-longest-path-directed-acyclic-graph/

一开始的想法是好好学习（照着打）一波，发现代码跑不了，问题应该是出在这一句：

list<AdjListNode> *adj;
Graph::Graph(int V) // Constructor
{
    this->V = V;
    adj = new list<AdjListNode>[V];
}

跑的时候好像是出现的堆错误，不知道是不是IDE的问题，我的是vs15，这个我想单独立个博客等以后来解决。这告诉我的道理是，看得懂别人的代码最好也还是跑一下，在实现的时候你才会真正地实现一些细节。还是感谢一波分享，除了上面说的还有几处new的地方都没有delete之外，算法什么应该都没问题。当然我贴的代码跑过了，下面是测试的代码：

test.cpp

#include "LongestPath.h"
#include <iostream>

using namespace std;

int main(void)
{
    graph g(6);
    g.addEdge(0, 1, 5);
    g.addEdge(0, 2, 3);
    g.addEdge(1, 3, 6);
    g.addEdge(1, 2, 2);
    g.addEdge(2, 4, 4);
    g.addEdge(2, 5, 2);
    g.addEdge(2, 3, 7);
    g.addEdge(3, 5, 1);
    g.addEdge(3, 4, -1);
    g.addEdge(4, 5, -2);

    int s = 1;
    cout << "Following are longest distances from "
        "source vertex " << s << " 
";
    g.longestPath(s);

    return 0;
}