hdu1874 畅通工程续 spfa/迪杰斯特拉

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题目链接:

http://acm.hdu.edu.cn/showproblem.php?pid=1874

题意:

题解:

卿学姐视频： http://www.bilibili.com/video/av4224493/

代码:

spfa：

#include <bits/stdc++.h>using namespace std;typedef long long ll;#define MS(a) memset(a,0,sizeof(a))#define MP make_pair#define PB push_backconst int INF = 0x3f3f3f3f;const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;inline ll read(){    ll x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}//////////////////////////////////////////////////////////////////////////const int maxn = 205+10;std::vector<pair<int,int> > E[maxn];int n,m;int d[maxn],inq[maxn];void init(){    for(int i=0; i<maxn; i++) E[i].clear();    for(int i=0; i<maxn; i++) inq[i] = 0;    for(int i=0; i<maxn; i++) d[i] = 1e9;}int main(){    while(cin >> n >> m){        init();        for(int i=0; i<m; i++){            int u,v,w; scanf("%d%d%d",&u,&v,&w);            E[u].push_back(MP(v,w));            E[v].push_back(MP(u,w));        }        int s,t;        scanf("%d%d",&s,&t);        queue<int> Q;        Q.push(s), d[s]=0, inq[s]=0;        while(!Q.empty()){            int now = Q.front();            Q.pop(); inq[now] = 0;            for(int i=0; i<(int)E[now].size(); i++){                int v = E[now][i].first, w = E[now][i].second;                if(d[now]+w < d[v]){                    d[v] = d[now]+w;                    if(inq[v]==1) continue;                    inq[v] = 1;                    Q.push(v);                }            }        }        if(d[t] == 1e9) printf("-1\n");        else printf("%d\n",d[t]);    }    return 0;}

dij：

#include <bits/stdc++.h>using namespace std;typedef long long ll;#define MS(a) memset(a,0,sizeof(a))#define MP make_pair#define PB push_backconst int INF = 0x3f3f3f3f;const ll INFLL = 0x3f3f3f3f3f3f3f3fLL;inline ll read(){    ll x=0,f=1;char ch=getchar();    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}    return x*f;}//////////////////////////////////////////////////////////////////////////const int maxn = 205+10;std::vector<pair<int,int> > E[maxn];int n,m;int d[maxn];void init(){    for(int i=0; i<maxn; i++) E[i].clear();    for(int i=0; i<maxn; i++) d[i] = 1e9;}int main(){    while(cin >> n >> m){        init();        for(int i=0; i<m; i++){            int u,v,w; scanf("%d%d%d",&u,&v,&w);            E[u].push_back(MP(v,w));            E[v].push_back(MP(u,w));        }        int s,t;        scanf("%d%d",&s,&t);        priority_queue<pair<int,int> > Q;        d[s]=0;        Q.push(MP(-d[s],s));        while(!Q.empty()){            int now = Q.top().second;            Q.pop();            for(int i=0; i<(int)E[now].size(); i++){                int v = E[now][i].first, w = E[now][i].second;                if(d[now]+w < d[v]){                    d[v] = d[now]+w;                    Q.push(MP(-d[v],v));                }            }        }        if(d[t] == 1e9) printf("-1\n");        else printf("%d\n",d[t]);    }    return 0;}

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