PAT A1018
A 1018 Public Bike Management
这个题目算是比较典型的一个。我分别用dfs，及dijkstra+dfs实现了一下。
dfs实现代码：
#include <cstdio>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstring>
using namespace std;
#define MAXNUM 510
#define CLR(a,b) memset(a,b,sizeof(a));
const int INF = 0x7f7f7f7f;
int C, N, Sp, M, dstDis = INF, tmpDstDis = , dstSendBikeNum = INF, dstBackBikeNum = INF;
vector<int> dstPathVec, tmpPathVec, routeVec[MAXNUM];
vector<int> bikeNumStaVec(MAXNUM,);
vector<int> visitFlagVec(MAXNUM,false);
int route[MAXNUM][MAXNUM];
void dfs(int u)
{
if(u == Sp && tmpDstDis <= dstDis)
{
int halfC = C/, tmpBikeNum = , tmpSendBikeNum = , tmpBackBikeNum = ;
for(int i = ; i < tmpPathVec.size(); ++ i)
{
tmpBikeNum += halfC-bikeNumStaVec[tmpPathVec[i]];
if(tmpBikeNum > )
{
tmpSendBikeNum += tmpBikeNum;
tmpBikeNum = ;
}
}
tmpBackBikeNum = -tmpBikeNum;
if(tmpDstDis < dstDis)
{
dstSendBikeNum = tmpSendBikeNum;
dstBackBikeNum = tmpBackBikeNum;
dstDis = tmpDstDis;
dstPathVec = tmpPathVec;
}
else if((tmpSendBikeNum < dstSendBikeNum) || (dstSendBikeNum == tmpSendBikeNum && dstBackBikeNum > tmpBackBikeNum))
{
dstSendBikeNum = tmpSendBikeNum;
dstBackBikeNum = tmpBackBikeNum;
dstDis = tmpDstDis;
dstPathVec = tmpPathVec;
}
return;
}
if(tmpDstDis > dstDis)
return;
for(auto it = routeVec[u].begin(); it != routeVec[u].end(); ++ it)
{
if(!visitFlagVec[*it])
{
visitFlagVec[*it] = true;
tmpPathVec.push_back(*it);
tmpDstDis += route[u][*it];
dfs(*it);
tmpDstDis -= route[u][*it];
tmpPathVec.pop_back();
visitFlagVec[*it] = false;
}
}
}
int main()
{
cin >> C >> N >> Sp >> M;
int tmpSt, tmpEnd, tmpDis;
for(int i = ; i <= N; ++i)
cin >> bikeNumStaVec[i];
CLR(route,0x7f);
while(M--)
{
cin >> tmpSt >> tmpEnd >> tmpDis;
route[tmpSt][tmpEnd] = tmpDis;
route[tmpEnd][tmpSt] = tmpDis;
routeVec[tmpSt].push_back(tmpEnd);
routeVec[tmpEnd].push_back(tmpSt);
}
visitFlagVec[] = true;
tmpPathVec.push_back();
dfs();
cout << dstSendBikeNum;
for(int i = ; i < dstPathVec.size(); ++i)
{
if(i == ) printf(" ");
else printf("->");
cout << dstPathVec[i];
}
cout << " " << dstBackBikeNum;
return ;
}
dijkstra和dfs实现代码
#include <cstdio>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstring>
using namespace std;
#define MAXNUM 510
#define CLR(a,b) memset(a,b,sizeof(a));
const int INF = 0x7f7f7f7f;
int C, N, Sp, M, dstSendBikeNum = INF, dstBackBikeNum = INF;
vector<int> dstPathVec, tmpPathVec, preRoute[MAXNUM];
vector<int> bikeNumStaVec(MAXNUM,);
vector<int> visitFlagVec(MAXNUM,false);
int dis[MAXNUM];
int route[MAXNUM][MAXNUM];
void dijkstra(int u)
{
dis[u] = ;
for(int i = ; i <= N; ++ i)
{
int tmpMinDis = INF, v = -;
for(int j = ; j <= N; ++ j)
{
if(!visitFlagVec[j] && dis[j] < tmpMinDis)
{
v = j;
tmpMinDis = dis[j];
}
}
if(v == - || v == Sp)
return;
visitFlagVec[v] = true;
for(int j = ; j <= N; ++ j)
{
if(!visitFlagVec[j] && dis[j] > dis[v] + route[v][j])
{
dis[j] = dis[v] + route[v][j];
preRoute[j].clear();
preRoute[j].push_back(v);
}
else if(!visitFlagVec[j] && dis[j] == dis[v] + route[v][j])
preRoute[j].push_back(v);
}
}
}
void dfs(int u)
{
if(u == )
{
tmpPathVec.push_back(u);
int halfC = C/, tmpBikeNum = , tmpSendBikeNum = , tmpBackBikeNum = ;
for(int i = tmpPathVec.size()-; i >= ; -- i)
{
tmpBikeNum += halfC-bikeNumStaVec[tmpPathVec[i]];
if(tmpBikeNum > )
{
tmpSendBikeNum += tmpBikeNum;
tmpBikeNum = ;
}
}
tmpBackBikeNum = -tmpBikeNum;
if((tmpSendBikeNum < dstSendBikeNum) || (dstSendBikeNum == tmpSendBikeNum && dstBackBikeNum > tmpBackBikeNum))
{
dstSendBikeNum = tmpSendBikeNum;
dstBackBikeNum = tmpBackBikeNum;
dstPathVec = tmpPathVec;
}
tmpPathVec.pop_back();
return;
}
tmpPathVec.push_back(u);
for(auto it = preRoute[u].begin(); it != preRoute[u].end(); ++ it)
dfs(*it);
tmpPathVec.pop_back();
}
int main()
{
cin >> C >> N >> Sp >> M;
int tmpSt, tmpEnd, tmpDis;
for(int i = ; i <= N; ++i)
cin >> bikeNumStaVec[i];
CLR(route,0x7f);
CLR(dis,0x7f);
while(M--)
{
cin >> tmpSt >> tmpEnd >> tmpDis;
route[tmpSt][tmpEnd] = tmpDis;
route[tmpEnd][tmpSt] = tmpDis;
}
dijkstra();
dfs(Sp);
cout << dstSendBikeNum;
reverse(dstPathVec.begin(), dstPathVec.end());
for(int i = ; i < dstPathVec.size(); ++i)
{
if(i == ) printf(" ");
else printf("->");
cout << dstPathVec[i];
}
cout << " " << dstBackBikeNum;
return ;
}
另：一种错误(dfs中，最后判断第二条件时出现了错误)
#include <cstdio>
#include <iostream>
#include <vector>
#include <algorithm>
#include <cmath>
#include <cstring>
using namespace std;
#define MAXNUM 510
#define CLR(a,b) memset(a,b,sizeof(a));
const int INF = 0x7f7f7f7f;
int C, N, Sp, M, dstSendBikeNum = INF, dstBackBikeNum = INF;
vector<int> dstPathVec, tmpPathVec, preRoute[MAXNUM];
vector<int> bikeNumStaVec(MAXNUM,);
vector<int> visitFlagVec(MAXNUM,false);
int dis[MAXNUM];
int route[MAXNUM][MAXNUM];
void dijkstra(int u)
{
dis[u] = ;
for(int i = ; i <= N; ++ i)
{
int tmpMinDis = INF, v = -;
for(int j = ; j <= N; ++ j)
{
if(!visitFlagVec[j] && dis[j] < tmpMinDis)
{
v = j;
tmpMinDis = dis[j];
}
}
if(v == - || v == Sp)
return;
visitFlagVec[v] = true;
for(int j = ; j <= N; ++ j)
{
if(!visitFlagVec[j] && dis[j] > dis[v] + route[v][j])
{
dis[j] = dis[v] + route[v][j];
preRoute[j].clear();
preRoute[j].push_back(v);
}
else if(!visitFlagVec[j] && dis[j] == dis[v] + route[v][j])
preRoute[j].push_back(v);
}
}
}
void dfs(int u)
{
if(u == )
{
tmpPathVec.push_back(u);
int tmpBikeNum = , tmpBackBikeNum = ;
for(int i = ; i < tmpPathVec.size()-; ++i)
{
tmpBikeNum += bikeNumStaVec[tmpPathVec[i]]-C/;
if(tmpBikeNum > )
{
tmpBackBikeNum += tmpBikeNum;
tmpBikeNum = ;
}
}
tmpBikeNum = -tmpBikeNum;
if(tmpBikeNum < dstSendBikeNum)
{
dstSendBikeNum = tmpBikeNum;
dstBackBikeNum = tmpBackBikeNum;
dstPathVec = tmpPathVec;
}
else if(tmpBikeNum == dstSendBikeNum && tmpBackBikeNum < dstBackBikeNum)
{
dstPathVec == tmpPathVec;
dstBackBikeNum = tmpBackBikeNum;
}
tmpPathVec.pop_back();
return;
}
tmpPathVec.push_back(u);
for(auto it = preRoute[u].begin(); it != preRoute[u].end(); ++ it)
dfs(*it);
tmpPathVec.pop_back();
}
int main()
{
cin >> C >> N >> Sp >> M;
int tmpSt, tmpEnd, tmpDis;
for(int i = ; i <= N; ++i)
cin >> bikeNumStaVec[i];
CLR(route,0x7f);
CLR(dis,0x7f);
while(M--)
{
cin >> tmpSt >> tmpEnd >> tmpDis;
route[tmpSt][tmpEnd] = tmpDis;
route[tmpEnd][tmpSt] = tmpDis;
}
dijkstra();
dfs(Sp);
cout << dstSendBikeNum;
reverse(dstPathVec.begin(), dstPathVec.end());
for(int i = ; i < dstPathVec.size(); ++i)
{
if(i == ) printf(" ");
else printf("->");
cout << dstPathVec[i];
}
cout << " " << dstBackBikeNum;
return ;
}
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