題目鏈接：https://vjudge.net/problem/HDU-4109

題目大意

有 N 個指令，標號從 0 ~ N - 1，和 M 個指令間的先后關系，每個關系都有一個權值 w，表示后一個指令在前一個指令開始時間之后 w 納秒才開始執行。現在要并發執行這些指令，問最少要多長時間才能執行完？

分析

關鍵路徑模板題，有多個源點和匯點，答案為所有匯點的最早開始時間的最大值。

代碼如下

1 #include <bits/stdc++.h> 2 using namespace std; 3 4 #define INIT() ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); 5 #define Rep(i,n) for (int i = 0; i < (n); ++i) 6 #define For(i,s,t) for (int i = (s); i <= (t); ++i) 7 #define rFor(i,t,s) for (int i = (t); i >= (s); --i) 8 #define ForLL(i, s, t) for (LL i = LL(s); i <= LL(t); ++i) 9 #define rForLL(i, t, s) for (LL i = LL(t); i >= LL(s); --i) 10 #define foreach(i,c) for (__typeof(c.begin()) i = c.begin(); i != c.end(); ++i) 11 #define rforeach(i,c) for (__typeof(c.rbegin()) i = c.rbegin(); i != c.rend(); ++i) 12 13 #define pr(x) cout << #x << " = " << x << " " 14 #define prln(x) cout << #x << " = " << x << endl 15 16 #define LOWBIT(x) ((x)&(-x)) 17 18 #define ALL(x) x.begin(),x.end() 19 #define INS(x) inserter(x,x.begin()) 20 #define UNIQUE(x) x.erase(unique(x.begin(), x.end()), x.end()) 21 #define REMOVE(x, c) x.erase(remove(x.begin(), x.end(), c), x.end()); // 刪去 x 中所有 c 22 #define TOLOWER(x) transform(x.begin(), x.end(), x.begin(),::tolower); 23 #define TOUPPER(x) transform(x.begin(), x.end(), x.begin(),::toupper); 24 25 #define ms0(a) memset(a,0,sizeof(a)) 26 #define msI(a) memset(a,0x7f,sizeof(a)) 27 #define msM(a) memset(a,-1,sizeof(a)) 28 29 #define MP make_pair 30 #define PB push_back 31 #define ft first 32 #define sd second 33 34 template<typename T1, typename T2> 35 istream &operator>>(istream &in, pair<T1, T2> &p) { 36 in >> p.first >> p.second; 37 return in; 38 } 39 40 template<typename T> 41 istream &operator>>(istream &in, vector<T> &v) { 42 for (auto &x: v) 43 in >> x; 44 return in; 45 } 46 47 template<typename T> 48 ostream &operator<<(ostream &out, vector<T> &v) { 49 Rep(i, v.size()) out << v[i] << " \n"[i == v.size()]; 50 return out; 51 } 52 53 template<typename T1, typename T2> 54 ostream &operator<<(ostream &out, const std::pair<T1, T2> &p) { 55 out << "[" << p.first << ", " << p.second << "]" << "\n"; 56 return out; 57 } 58 59 inline int gc(){ 60 static const int BUF = 1e7; 61 static char buf[BUF], *bg = buf + BUF, *ed = bg; 62 63 if(bg == ed) fread(bg = buf, 1, BUF, stdin); 64 return *bg++; 65 } 66 67 inline int ri(){ 68 int x = 0, f = 1, c = gc(); 69 for(; c<48||c>57; f = c=='-'?-1:f, c=gc()); 70 for(; c>47&&c<58; x = x*10 + c - 48, c=gc()); 71 return x*f; 72 } 73 74 template<class T> 75 inline string toString(T x) { 76 ostringstream sout; 77 sout << x; 78 return sout.str(); 79 } 80 81 inline int toInt(string s) { 82 int v; 83 istringstream sin(s); 84 sin >> v; 85 return v; 86 } 87 88 //min <= aim <= max 89 template<typename T> 90 inline bool BETWEEN(const T aim, const T min, const T max) { 91 return min <= aim && aim <= max; 92 } 93 94 typedef long long LL; 95 typedef unsigned long long uLL; 96 typedef vector< int > VI; 97 typedef vector< bool > VB; 98 typedef vector< char > VC; 99 typedef vector< double > VD; 100 typedef vector< string > VS; 101 typedef vector< LL > VL; 102 typedef vector< VI > VVI; 103 typedef vector< VB > VVB; 104 typedef vector< VS > VVS; 105 typedef vector< VL > VVL; 106 typedef vector< VVI > VVVI; 107 typedef vector< VVL > VVVL; 108 typedef pair< int, int > PII; 109 typedef pair< LL, LL > PLL; 110 typedef pair< int, string > PIS; 111 typedef pair< string, int > PSI; 112 typedef pair< string, string > PSS; 113 typedef pair< double, double > PDD; 114 typedef vector< PII > VPII; 115 typedef vector< PLL > VPLL; 116 typedef vector< VPII > VVPII; 117 typedef vector< VPLL > VVPLL; 118 typedef vector< VS > VVS; 119 typedef map< int, int > MII; 120 typedef unordered_map< int, int > uMII; 121 typedef map< LL, LL > MLL; 122 typedef map< string, int > MSI; 123 typedef map< int, string > MIS; 124 typedef set< int > SI; 125 typedef stack< int > SKI; 126 typedef queue< int > QI; 127 typedef priority_queue< int > PQIMax; 128 typedef priority_queue< int, VI, greater< int > > PQIMin; 129 const double EPS = 1e-8; 130 const LL inf = 0x7fffffff; 131 const LL infLL = 0x7fffffffffffffffLL; 132 const LL mod = 1e9 + 7; 133 const int maxN = 1e3 + 7; 134 const LL ONE = 1; 135 const LL evenBits = 0xaaaaaaaaaaaaaaaa; 136 const LL oddBits = 0x5555555555555555; 137 138 struct Edge{ 139 int from, to, w; 140 int et, lt; 141 }; 142 143 istream& operator>> (istream& in, Edge &x) { 144 in >> x.from >> x.to >> x.w; 145 return in; 146 } 147 148 struct Vertex{ 149 int in, out, value; 150 VI next, prev; 151 int et, lt; 152 153 void clear() { 154 value = in = out = 0; 155 next.clear(); 156 prev.clear(); 157 et = 0; 158 lt = inf; 159 } 160 }; 161 162 int N, M, ans; 163 Vertex V[maxN]; 164 vector< Edge > E; 165 VI topo; 166 167 void addEdge(Edge &x) { 168 V[x.from].next.PB(E.size()); 169 V[x.to].prev.PB(E.size()); 170 ++V[x.to].in; 171 ++V[x.from].out; 172 E.PB(x); 173 } 174 175 void init() { 176 For(i, 1, N) V[i].clear(); 177 E.clear(); 178 topo.clear(); 179 ans = 0; 180 } 181 182 void TopoSort() { 183 SKI sk; 184 For(i, 1, N) if(!V[i].in) sk.push(i); 185 186 while(!sk.empty()) { 187 int tmp = sk.top(); sk.pop(); 188 189 topo.PB(tmp); 190 Rep(i, V[tmp].next.size()) { 191 Edge &e = E[V[tmp].next[i]]; 192 if(!--V[e.to].in) sk.push(e.to); 193 V[e.to].et = max(V[e.to].et, V[e.from].et + e.w); // 在拓撲排序的同時計算每個節點的最早發生時間 194 } 195 } 196 } 197 198 int main(){ 199 //freopen("MyOutput.txt","w",stdout); 200 //freopen("input.txt","r",stdin); 201 INIT(); 202 while(cin >> N >> M) { 203 init(); 204 Rep(i, M) { 205 Edge t; 206 cin >> t; 207 ++t.from; 208 ++t.to; 209 addEdge(t); 210 } 211 TopoSort(); 212 For(i, 1, N) if(!V[i].out) ans = max(ans, V[i].et); 213 cout << ans + 1 << endl; 214 } 215 return 0; 216 } View Code

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轉載于:https://www.cnblogs.com/zaq19970105/p/11319841.html

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