POJ 1287 Networking

末蓝、 2021-10-18 07:36 203阅读 0赞

题目链接：[https://vjudge.net/problem/POJ-1287][https_vjudge.net_problem_POJ-1287]

### 题目大意 ###

略。

### 分析 ###

最小生成树模板题。这题图为稀疏图，应选择 Kruskal 算法。

### 代码如下 ###

![ContractedBlock.gif][] ![ExpandedBlockStart.gif][]

1 #include <cmath>
      2 #include <ctime>
      3 #include <iostream>
      4 #include <string>
      5 #include <vector>
      6 #include <cstdio>
      7 #include <cstdlib>
      8 #include <cstring>
      9 #include <queue>
     10 #include <map>
     11 #include <set>
     12 #include <algorithm>
     13 #include <cctype>
     14 #include <stack>
     15 #include <deque>
     16 #include <list>
     17 #include <sstream>
     18 #include <cassert>
     19 using namespace std;
     20  
     21 #define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0);
     22 #define Rep(i,n) for (int i = 0; i < (n); ++i)
     23 #define For(i,s,t) for (int i = (s); i <= (t); ++i)
     24 #define rFor(i,t,s) for (int i = (t); i >= (s); --i)
     25 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i)
     26 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i)
     27 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i)
     28 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i)
     29  
     30 #define pr(x) cout << #x << " = " << x << "  "
     31 #define prln(x) cout << #x << " = " << x << endl
     32  
     33 #define LOWBIT(x) ((x)&(-x))
     34  
     35 #define ALL(x) x.begin(),x.end()
     36 #define INS(x) inserter(x,x.begin())
     37 #define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end())
     38 #define REMOVE(x, c) x.erase(remove(x.begin(), x.end(), c), x.end()); // 删去 x 中所有 c 
     39 #define TOLOWER(x) transform(x.begin(), x.end(), x.begin(),::tolower);
     40 #define TOUPPER(x) transform(x.begin(), x.end(), x.begin(),::toupper);
     41  
     42 #define ms0(a) memset(a,0,sizeof(a))
     43 #define msI(a) memset(a,0x3f,sizeof(a))
     44 #define msM(a) memset(a,-1,sizeof(a))
     45 
     46 #define MP make_pair
     47 #define PB push_back
     48 #define ft first
     49 #define sd second
     50  
     51 template<typename T1, typename T2>
     52 istream &operator>>(istream &in, pair<T1, T2> &p) {
     53     in >> p.first >> p.second;
     54     return in;
     55 }
     56  
     57 template<typename T>
     58 istream &operator>>(istream &in, vector<T> &v) {
     59     for (auto &x: v)
     60         in >> x;
     61     return in;
     62 }
     63  
     64 template<typename T1, typename T2>
     65 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) {
     66     out << "[" << p.first << ", " << p.second << "]" << "\n";
     67     return out;
     68 }
     69 
     70 inline int gc(){
     71     static const int BUF = 1e7;
     72     static char buf[BUF], *bg = buf + BUF, *ed = bg;
     73     
     74     if(bg == ed) fread(bg = buf, 1, BUF, stdin);
     75     return *bg++;
     76 } 
     77 
     78 inline int ri(){
     79     int x = 0, f = 1, c = gc();
     80     for(; c<48||c>57; f = c=='-'?-1:f, c=gc());
     81     for(; c>47&&c<58; x = x*10 + c - 48, c=gc());
     82     return x*f;
     83 }
     84 
     85 template<class T>
     86 inline string toString(T x) {
     87     ostringstream sout;
     88     sout << x;
     89     return sout.str();
     90 }
     91 
     92 inline int toInt(string s) {
     93     int v;
     94     istringstream sin(s);
     95     sin >> v;
     96     return v;
     97 }
     98 
     99 //min <= aim <= max
    100 template<typename T>
    101 inline bool BETWEEN(const T aim, const T min, const T max) {
    102     return min <= aim && aim <= max;
    103 }
    104  
    105 typedef long long LL;
    106 typedef unsigned long long uLL;
    107 typedef pair< double, double > PDD;
    108 typedef pair< int, int > PII;
    109 typedef pair< int, PII > PIPII;
    110 typedef pair< string, int > PSI;
    111 typedef pair< int, PSI > PIPSI;
    112 typedef set< int > SI;
    113 typedef set< PII > SPII;
    114 typedef vector< int > VI;
    115 typedef vector< double > VD;
    116 typedef vector< VI > VVI;
    117 typedef vector< SI > VSI;
    118 typedef vector< PII > VPII;
    119 typedef map< int, int > MII;
    120 typedef map< LL, int > MLLI;
    121 typedef map< int, string > MIS;
    122 typedef map< int, PII > MIPII;
    123 typedef map< PII, int > MPIII;
    124 typedef map< string, int > MSI;
    125 typedef map< string, string > MSS;
    126 typedef map< PII, string > MPIIS;
    127 typedef map< PII, PII > MPIIPII;
    128 typedef multimap< int, int > MMII;
    129 typedef multimap< string, int > MMSI;
    130 //typedef unordered_map< int, int > uMII;
    131 typedef pair< LL, LL > PLL;
    132 typedef vector< LL > VL;
    133 typedef vector< VL > VVL;
    134 typedef priority_queue< int > PQIMax;
    135 typedef priority_queue< int, VI, greater< int > > PQIMin;
    136 const double EPS = 1e-8;
    137 const LL inf = 0x3fffffff;
    138 const LL infLL = 0x3fffffffffffffffLL;
    139 const LL mod = 1e9 + 7;
    140 const int maxN = 5e1 + 7;
    141 const LL ONE = 1;
    142 const LL evenBits = 0xaaaaaaaaaaaaaaaa;
    143 const LL oddBits = 0x5555555555555555;
    144 
    145 struct Edge{
    146     int from, to, w;
    147     
    148     inline bool operator< (const Edge &x) const {
    149         return w < x.w;
    150     }
    151 }; 
    152 
    153 istream& operator>> (istream &in, Edge &x) {
    154     in >> x.from >> x.to >> x.w;
    155     return in;
    156 }
    157 
    158 int N, M, ans; 
    159 vector< Edge > E;
    160 
    161 // 并查集 
    162 int f[maxN];
    163 
    164 inline int Find(int x) {
    165     while(x != f[x]) x = f[x] = f[f[x]];
    166     return x;
    167 }
    168 
    169 inline void Union(int x, int y) {
    170     f[y] = f[x];
    171 }
    172 
    173 void init() {
    174     For(i, 1, N) f[i] = i;
    175     E.clear();
    176     
    177     ans = 0;
    178 }
    179 
    180 void Kruskal() {
    181     int cnt = 1;
    182     sort(ALL(E));
    183     
    184     Rep(i, E.size()) {
    185         if(cnt >= N) break;
    186         int x = Find(E[i].from), y = Find(E[i].to);
    187         
    188         if(x != y) {
    189             ++cnt;
    190             Union(x, y);
    191             ans += E[i].w;
    192         }
    193     }
    194 }
    195 
    196 int main(){
    197     //freopen("MyOutput.txt","w",stdout);
    198     //freopen("input.txt","r",stdin);
    199     INIT();
    200     while(cin >> N && N) {
    201         init();
    202         cin >> M;
    203         For(i, 1, M) {
    204             Edge t;
    205             cin >> t;
    206             E.PB(t);
    207         }
    208         
    209         Kruskal();
    210         
    211         cout << ans << endl;
    212     }
    213     return 0;
    214 }

转载于:https://www.cnblogs.com/zaq19970105/p/11302374.html

[https_vjudge.net_problem_POJ-1287]: https://vjudge.net/problem/POJ-1287
[ContractedBlock.gif]: https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20211018/28b929f3ef154b05b12bbec71acd50bc.png