PAT 1076. Forwards on Weibo (30)

题目地址：http://pat.zju.edu.cn/contests/pat-a-practise/1076

此题考查图的遍历操作：

本来我个人觉得可以用dfs的，但是不知何故，有两个case没有过，贴出代码，望指出错误之处:

#include <cstdio>

#include <map>

#include <vector>

#include <memory.h>

using namespace std;

const int NUM=1001;

bool visited[NUM];

int forwards;

map<int,vector<int> > adjlist;
void reset()

{

    memset(visited,false,sizeof(bool)*NUM);

    forwards=0;

}
void dfs(int sourceNode,int indLevel,int L)

{

    if(indLevel>L)

        return;

    for(vector<int>::iterator iter=adjlist[sourceNode].begin();iter!=adjlist[sourceNode].end();++iter)

    {

        if(!visited[*iter])

        {

            ++forwards;

            visited[*iter]=true;

            dfs(*iter,indLevel+1,L);

        }

    }

}
int _tmain(int argc, _TCHAR* argv[])

{

    int N,L;

    scanf("%d %d",&N,&L);

    if(L>6)

        L=6;

    int i,Mi,j,followed;

    for(i=1;i<=N;++i)

    {

        scanf("%d",&Mi);

        for(j=0;j<Mi;++j)

        {

            scanf("%d",&followed);

            adjlist[followed].push_back(i);

        }

    }

    int K,query;

    scanf("%d",&K);

    for(i=0;i<K;++i)

    {

        scanf("%d",&query);

        reset();

        visited[query]=true;

        dfs(query,1,L);

        printf("%d\n",forwards);

    }

    return 0;

}

后来换了bfs后，AC了：

#include <cstdio>

#include <map>

#include <vector>

#include <queue>

#include <memory.h>

using namespace std;

const int NUM=1001;
bool  hasForward[NUM];

int forwards;

map<int,vector<int> > adjlist;

queue<int> recordQueue;
void reset()

{

    memset(hasForward,false,sizeof(bool)*NUM);

    forwards=0;

    while(!recordQueue.empty())

        recordQueue.pop();

}
void bfs(int query,int level)

{

    int curLevel=1;

    hasForward[query]=true;

    recordQueue.push(query);

    int endOfLevel=recordQueue.back();

    int cur;

    while(!recordQueue.empty()&&curLevel<=level)

    {

        cur=recordQueue.front();

        recordQueue.pop();

        for(vector<int>::iterator iter=adjlist[cur].begin();iter!=adjlist[cur].end();++iter)

        {

            if(!hasForward[*iter])

            {

                recordQueue.push(*iter);

                ++forwards;

                hasForward[*iter]=true;

            }

        }

        if(cur==endOfLevel)

        {

            ++curLevel;

            endOfLevel=recordQueue.back();

        }

    }

}

int _tmain(int argc, _TCHAR* argv[])

{

    int N,L;

    scanf("%d %d",&N,&L);

    if(L>6)

        L=6;

    int i,j;

    int Mi,followed;

    for(i=1;i<=N;++i)

    {

        scanf("%d",&Mi);

        for(j=0;j<Mi;++j)

        {

            scanf("%d",&followed);

            adjlist[followed].push_back(i);

        }

    }

    int K,query;

    scanf("%d",&K);

    for(i=0;i<K;++i)

    {

        scanf("%d",&query);

        reset();

        bfs(query,L);

        printf("%d\n",forwards);

    }

    return 0;

}

PAT 1076. Forwards on Weibo (30),布布扣,bubuko.com