Zoj 1455 Schedule Problem difference Constraint

Set d [I] to the start time of the I-th job:

Fas a B: d [a] + time [a]> = d [B]

Faf a B: d [a] + time [a]> = d [B] + time [B]

Saf a B: d [a]> = d [B] + time [B]

Sas a B: d [a]> = d [B]

Also, d [I]> = 0, that is, d [I]-d [0]> = 0

Start searching with 0 as the Source Vertex, and 0 as the supersource Vertex

 

# Include <iostream> # include <queue> # include <cstring> # include <cstdio> using namespace STD; const int max = 100000; const int n = 10000; const int INF = 1000000000; struct node {int V; int cost; int next ;}; node [Max]; int CNT [N]; int adj [N]; bool in_q [N]; int d [N], times [N]; int N; int size; void add_edge (int u, int V, int cost) {node [size]. V = V; node [size]. cost = cost; node [size]. next = adj [u]; adj [u] = size ++;} Bool spfa () {queue <int> q; memset (CNT, 0, sizeof (CNT); memset (in_q, false, sizeof (in_q )); for (INT I = 0; I <= N; I ++) d [I] =-INF; d [0] = 0; q. push (0); in_q [0] = true; int U, V, W; while (! Q. Empty () {u = Q. Front (); q. Pop (); in_q [u] = false; For (INT I = adj [u]; I! =-1; I = node [I]. next) {v = node [I]. v; W = node [I]. cost; If (d [v] <D [u] + W) {d [v] = d [u] + W; If (! In_q [v]) {in_q [v] = true; q. push (V); If (++ CNT [v]> N) return false ;}}}return true;} int main () {char C [20]; int A, B; INT cases = 1; while (scanf ("% d", & N )! = EOF) {If (n = 0) break; size = 0; For (INT I = 0; I <= N; I ++) adj [I] =-1; for (INT I = 1; I <= N; I ++) scanf ("% d", & Times [I]); while (1) {getchar (); scanf ("% s", c); If (strcmp (C, "#") = 0) break; else if (strcmp (C, "fas") = 0) {scanf ("% d", & A, & B); add_edge (B,, -Times [a]);} else if (strcmp (C, "FAF") = 0) {scanf ("% d", & A, & B ); add_edge (B, A, times [B]-Times [a]);} else if (strcmp (C, "SAF") = 0) {scanf ("% d", & A, & B); add_edge (B, A, times [B]);} else if (strcmp (C, "SAS") = 0) {scanf ("% d", & A, & B); add_edge (B, A, 0 );}} for (INT I = 1; I <= N; I ++) add_edge (0, I, 0); printf ("case % d: \ n ", cases ++); If (spfa () {for (INT I = 1; I <= N; I ++) printf ("% d \ n ", i, d [I]);} elseprintf ("impossible \ n"); printf ("\ n");} return 0 ;}