1599 - Ideal Path

来源：互联网发布：冰毒工具玻璃头淘宝编辑：程序博客网时间：2024/04/30 19:06
2个dfs遍历，第一个用的优先队列~第二个直接BFS就行了
不要把这题想的太复杂了，尤其是第二个保存路径的，只要记录每次走到哪个位置就行了
#include<cstdio>#include<algorithm>#include<cstring>#include<iostream>#include<stack>#include<queue>#include<map>#include<vector>using namespace std;#define INF 1 << 30#define MAXD 100000 + 10#define MAX_SIZE 400000 + 10typedef pair<int,int> pill;int n,m;int Right[MAX_SIZE];int Color[MAX_SIZE];int dist[MAXD]; /*其余点到终点的距离*/int ans[MAXD];vector<int>G[MAXD];struct State{    int pos;        /*当前位置*/    vector<int>arr; /*当前路径*/};void GetDistance_dfs(int u,int d){  /*寻找每个点到终点的最短距离*/    priority_queue<pill,vector<pill>,greater<pill> >q;    q.push(make_pair(0,n));    int vis[MAXD] = {0};    vis[n] = 1;    while(!q.empty()){        pill t = q.top(); q.pop();        int _dist = t.first;        int pos  = t.second;        for(int i = 0 ; i < G[pos].size(); i++){            int l = G[pos][i];            int r = Right[l];            if(!vis[r]){                vis[r] = 1;                dist[r] = _dist + 1;                q.push(make_pair(_dist + 1,r));            }         }    }    return ;}void GetPrintf_dfs(){    queue<int>q;    q.push(1);    int vis[MAXD] = {0};    while(!q.empty()){        int pos = q.front();        q.pop();        int _MIN = INF;        for(int i = 0 ; i < G[pos].size(); i++){            int l = G[pos][i];            int r = Right[l];            int c = Color[l];            if(dist[pos] - 1 == dist[r] && c < _MIN){   /*先选出最短路径*/                  _MIN = c;            }        }        int now_step =  dist[1] - dist[pos];        if(ans[now_step] == -1)            ans[now_step] = _MIN;        else            ans[now_step] = min(ans[now_step],_MIN);        for(int i = 0 ; i < G[pos].size(); i++){            int l = G[pos][i];            int r = Right[l];            int c = Color[l];            if(!vis[r] && _MIN == c && dist[r] == dist[pos] - 1){                q.push(r);                vis[r] = 1;                /*这里不要忘了标记，去除重复，因为如果一个节点之前走到过，那么是不可能再走回来的！*/            }        }    }}int main(){    while(scanf("%d%d",&n,&m) != EOF){        for(int i = 1 ; i <= n ; i++) G[i].clear();  /*初始化*/        for(int i = 1 ; i <= n ; i++) dist[i] = INF;        dist[n] = 0;        for(int i = 1 ; i <= m ; i++){            int x,y,z;            scanf("%d%d%d",&x,&y,&z);            if(x != y){            G[x].push_back(i);            Right[i] = y;            Color[i] = z;            G[y].push_back(i + m);            Right[i + m] = x;            Color[i + m] = z;            }        }        GetDistance_dfs(n,0);        memset(ans,-1,sizeof(ans));        GetPrintf_dfs();        printf("%d\n",dist[1]);        for(int i = 0 ; i < dist[1]; i++){            printf("%d",ans[i]);            if(i < dist[1] - 1)                printf(" ");        }        printf("\n");    }    return 0;}
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