标签：should nis 也有 ensure nat char sizeof 关键路径 content
1 关键路径
InputThe input consists several testcases.
The first line has two integers N, M (N <= 1000, M <= 10000), means that there are N instructions and M dependent relations.
The following M lines, each contains three integers X, Y , Z, means the Safe Distance between X and Y is Z, and Y should run after X. The instructions are numbered from 0 to N - 1.
OutputPrint one integer, the minimum time the CPU needs to run.
Sample Input
5 2 1 2 1 3 4 1
Sample Output
2
Hint
In the 1st ns, instruction 0, 1 and 3 are executed; In the 2nd ns, instruction 2 and 4 are executed. So the answer should be 2.
题意：有许多个任务，需要完成它们，有先后顺序，并且也有间隔时间，比如AB间隔时间为t，则t之后才能做B，对于做每个没有关联的任务，你可以同时完成它们，需1ns（时间），
题解：很容易就看出来这是个拓扑排序了，利用bfs拓扑排序，只有入度为0才进队，并且在入队时更新最大距离（关键路径就是求图上最长路），但有一个注意点，就是刚开始找入度为0的点，
你需要先给它们dis值置为1，因为完成它们需1ns,关键路径也可用spfa求最长路，权值取反，求最短路
1 var 2 head,next,a,rd,q,dis,w:array[0..50000]of longint; 3 e,ans,i,j,x,y,z,n,m:longint; 4 function max(x,y:longint):longint; 5 begin 6 if x>y then exit(x) else exit(y); 7 end; 8 procedure add(x,y,z:longint); 9 begin 10 inc(e);a[e]:=y;next[e]:=head[x];head[x]:=e; w[i]:=z; 11 end; 12 procedure bfs; 13 var h,t,i,v:longint; 14 begin 15 h:=0;t:=0; 16 for i:=0 to n-1 do 17 begin 18 if rd[i]=0 then begin inc(t); q[t]:=i; rd[i]:=-1;dis[i]:=1; end; 19 end; 20 while h<t do 21 begin 22 inc(h); 23 i:=head[q[h]]; 24 while i>0 do 25 begin 26 v:=a[i]; 27 dis[v]:=max(dis[v],dis[q[h]]+w[i]); 28 dec(rd[v]); 29 if rd[v]=0 then begin inc(t); q[t]:=v; rd[v]:=-1;end; 30 i:=next[i]; 31 end; 32 end; 33 // for i:=0 to n-1 do write(dis[i],‘ ‘); 34 end; 35 begin 36 while not eof do 37 begin 38 fillchar(a,sizeof(a),0); 39 fillchar(next,sizeof(next),0); 40 fillchar(head,sizeof(head),0); 41 fillchar(rd,sizeof(rd),0); 42 fillchar(w,sizeof(w),0); 43 fillchar(dis,sizeof(dis),0); 44 fillchar(q,sizeof(q),0); 45 ans:=0; e:=0; 46 readln(n,m); 47 for i:=1 to m do 48 begin 49 readln(x,y,z); 50 add(x,y,z); 51 inc(rd[y]); 52 end; 53 bfs; 54 for i:=0 to n-1 do ans:=max(ans,dis[i]); 55 writeln(ans); 56 end; 57 end.
标签：should nis 也有 ensure nat char sizeof 关键路径 content
原文地址：https://www.cnblogs.com/brilliant107/p/9416249.html
