HDU6386 Age of Moyu【dfs+bfs】

最新推荐文章于 2020-10-05 21:30:16 发布

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本文介绍了一种基于图遍历的算法实现，该算法通过深度优先搜索(DFS)与广度优先搜索(BFS)相结合的方法解决特定类型的路径寻找问题。通过对输入的边进行处理，并利用队列和结构体辅助存储节点信息，最终找到从起点到终点的最短路径。

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晚点补题解

#include <bits/stdc++.h>
#include <queue>
#define INF 0x3f3f3f3f
using namespace std;

const int MAXN = 200005;

int head[MAXN],dis[MAXN];
int look[MAXN];//vis
int n,m,cas,ans;
int u,v,w;
queue <int> q;

struct Edge {
	int u,v,w,next,vis;
	void set(int u, int v, int w) {
		this->u = u;
		this->v = v;
		this->w = w;
	}
} edge[MAXN<<2];

void addEdge(int u, int v, int w) {
	edge[cas].set(u,v,w);
	edge[cas].next = head[u];
	edge[cas].vis = 0;
	head[u] = cas++;
}

void dfs(int rt, int cl, int num) {
	int i, j;
	if(rt == n) {
		ans = num;
		return;
	}
	if(!look[rt]) {
		look[rt] = 1;
		dis[rt] = num;
		q.push(rt);
	}
	for(i = head[rt]; i != -1; i = edge[i].next) {
		if(edge[i].vis) continue;
		if(edge[i].w == cl) {
			edge[i].vis = 1;
			dfs(edge[i].v,cl,num);
		}
	}
	return;
}

int bfs() {
	while(!q.empty()) q.pop();
	q.push(1);
	dis[1] = 0;
	look[1] = 1;
	while(!q.empty()) {
		int now = q.front();
		q.pop();
		for(int i = head[now]; i != -1; i = edge[i].next) {
			if(edge[i].vis) continue;
			v = edge[i].v;
			edge[i].vis = 1;
			dfs(v,edge[i].w,dis[now]+1);
			if(ans>0) break;
		}
		if(ans > 0) break;
	}
	return ans;
}

int main() {
	while(~scanf("%d%d",&n,&m)) {
		cas = 0;
		memset(head, -1, sizeof(head));
		memset(look, 0, sizeof(look));
		memset(dis, INF, sizeof(dis));
		for(int i = 1; i <= m; i++) {
			scanf("%d%d%d",&u,&v,&w);
			addEdge(u,v,w);
			addEdge(v,u,w);
		}
		ans = -1;
		ans = bfs();
		printf("%d\n",ans);
	}
	return 0;
}