# Bellman_ford ultraviolet 11280-flying to Fredericton

Source: Internet
Author: User

// Take A Look At bellman_ford: in fact, he is constructing a shortest path tree with the source point as the root through constant relaxation, in the original algorithm, after the end of the I-th relaxation, the shortest distance from the root node to the point with the node length not greater than I will be generated)

// Note that the unoptimized bellman does not guarantee that every distance after I is relaxed is the shortest path length of I, because it is out of order when the side is relaxed, the result may be greater than I.

// Use spfa to mark the distance between points. Note that we need to mark two-dimensional arrays ,, obviously, we cannot determine who will make the final result better when a shorter weight and a shorter short circuit are updated to the adjacent contacts.

# Include <iostream> <br/> # include <string> <br/> # include <map> <br/> # include <vector> <br/> # include <memory. h> <br/> # include <cstdio> <br/> # include <cmath> <br/> # include <algorithm> <br/> using namespace STD; <br/> const int max = 1005, INF = 1 <30; <br/> struct state {<br/> int DIS, num; <br/> }; </P> <p> int n, m, U [Max * 10], V [Max * 10], W [Max * 10], <br/> d [Max] [Max], first [Max], next [Max * 10]; </P> <p> Map <string, int> my Map; <br/> bool INQ [Max] [Max]; <br/> state Q [Max * max], temp, out; </P> <p> void bellman_ford (const Int & Len) {<br/> memset (INQ, 0, sizeof (INQ )); <br/> int front = 1, rear = 1; <br/> int U, V, W, minval = inf, <br/> sta = 0, end = n-1, DIS; </P> <p> for (INT I = 0; I <n; I ++) <br/> for (Int J = 0; j <= Len; j ++) {<br/> If (! I) <br/> d [I] [J] = 0; <br/> else <br/> d [I] [J] = inf; <br/>}</P> <p> temp. num = sta; <br/> temp. dis = 0; </P> <p> INQ [temp. num] [temp. dis] = 1; </P> <p> q [rear ++] = temp; </P> <p> while (front <rear) {</P> <p> out = Q [Front ++]; <br/> U = out. num; <br/> Dis = out. DIS; </P> <p> for (int e = first [u]; e! =-1; E = next [e]) {</P> <p> V = V [E]; W = W [E]; </P> <p> If (d [v] [DIS + 1]> d [u] [dis] + W <br/> & DIS + 1 <= Len) {</P> <p> d [v] [DIS + 1] = d [u] [dis] + W; </P> <p> If (! INQ [v] [DIS + 1]) {<br/> INQ [v] [DIS + 1] = 1; <br/> temp. num = V; temp. dis = DIS + 1; <br/> q [rear ++] = temp; <br/>}</P> <p> for (INT I = 0; I <= Len; I ++) {<br/> If (d [end] [I] <minval) <br/> minval = d [end] [I]; <br/>}</P> <p> If (minval! = Inf) <br/> cout <"Total Cost of flight (s) is \$" <minval <Endl; <br/> else <br/> cout <"no satisfactory flights" <Endl; <br/>}</P> <p> int main () <br/>{< br/> freopen ("I .txt", "r", stdin); </P> <p> int ncase, T, num = 0, Q; <br/> string S, Su, SV; <br/> CIN> ncase; <br/> while (ncase --) {</P> <p> memset (first,-1, sizeof (first); <br/> If (Num ++) <br/> cout <Endl; <br/> cout <"Scenario #" <num <Endl; <br/> mymap. clear (); </P> <p> CIN> N; </P> <p> for (INT I = 0; I <n; I ++) {<br/> CIN> S; <br/> mymap [s] = I; <br/>}</P> <p> CIN> m; </P> <p> for (INT I = 0; I <m; I ++) {<br/> CIN> su> Sv; <br/> U [I] = mymap [Su]; V [I] = mymap [SV]; <br/> CIN> W [I]; </P> <p> next [I] = first [U [I]; <br/> first [U [I] = I; </P> <p >}</P> <p> CIN> q; <br/> while (Q --) {<br/> CIN> T; <br/> If (T <0) t = 0; <br/> If (T> N) t = n; <br/> bellman_ford (t + 1 ); <br/>}</P> <p >}< br/> return 0; <br/>}</P> <p>

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