技術標籤：日常練習演算法dfsc++圖搜尋

給定一個起點和一幅圖，搜尋到目標點的路徑

方法

在搜尋過程中維護一個父親陣列，將當前節點記為他那些尚未標記的鄰接節點的父親，本質是一棵樹。列印路徑是從終點迭代找他的父親，可以用棧儲存，最後棧頂是起點，依次彈出就是路徑。這裡我採用了list的頭插法，效果一樣。

Path.h

#pragma once
#include<queue>
#include"Graph.h"

/********************如無必要，勿增實體**********************/
class Paths
{
public
 
:
	Paths(Graph& G, int s,bool isBfs=true);

	bool hasPathto(int v);
	list<int> pathTo(int v);

private:
	vector<bool>* m_marked = nullptr;
	vector<int>* m_father = nullptr;
	int m_source = 0;

	void dfs(Graph& G, int v);
	void bfs(Graph& G, int v);
};

void testForPaths(
 
);

Paths.cpp

#include "Paths.h"

Paths::Paths(Graph& G, int s,bool isBfs):m_source(s)
{
	int n = G.V();
	m_marked = new vector<bool>(n, false);
	m_father = new vector<int>(n, -1);
	
	isBfs ? bfs(G, s) : dfs(G, s);
}

bool Paths::hasPathto(int v)
{
	return m_marked->at(v)
 
;
}


list<int> Paths::pathTo(int v)
{
	list<int>* ans = new list<int>();
	ans->push_front(v);//頭插法
	while (m_father->at(v) != -1) {//未到起點
		v = m_father->at(v);
		ans->push_front(v);
	}
	return *ans;
}


inline
void Paths::dfs(Graph& G, int v)
{
	m_marked->at(v) = true;
	for (auto& next : G.adj(v)) {
		if (!m_marked->at(next)) {
			m_father->at(next) = v;//記錄自己的父親
			dfs(G, next);
		}
	}
}




inline
void Paths::bfs(Graph& G, int v) {
	m_marked->at(v) = true;

	queue<int> Q;
	Q.push(v);

	while (!Q.empty()) {
		int front = Q.front(); Q.pop();

		for (auto& next : G.adj(front)) {
			if (!(*m_marked)[next]) {
				m_marked->at(next) = true;
				m_father->at(next) = front;//記錄父親
				Q.push(next);//相當於遞迴入棧
			}
		}
	}
}

void testForPaths()
{
	Graph G("data.txt");
	int source = 0;
	Paths path(G, source,true);

	for (int i = 0; i < G.V(); ++i) {
		printf_s("%2d to %2d : ", source, i);
		if (path.hasPathto(i)) {
			for (auto& v : path.pathTo(i)) {
				if (source == v) printf_s("%2d", source);
				else printf_s(" -%2d", v);
			}
			printf_s("\n");
		}else
			printf_s(" unconnected.\n");
	}

}

data.txt

12
16
8 4
2 3
1 11
3 6
0 6
10 3
7 11
7 8
8 11
0 2
5 2
6 2
5 10
5 0
8 1
4 1

圖的標頭檔案在這裡：從檔案讀取構建圖https://blog.csdn.net/qq_34890856/article/details/112938237