Stack-optimized Dijkstra

I knocked on the heap again and got a deeper understanding.

Insert operation: add elements to the end of the array to automatically move up.

Delete operation: Move the elements at the end of the array to the root node and sink to a small subnode.

In the impression, the priority queue is a pointer + tedious operation. In fact, the code can be simplified to six rows.

It is only a little less than spfa, rank2's shortest path algorithm.

# Include <stdio. h> <br/> # include <stdlib. h> <br/> # include <vector> <br/> using namespace STD; <br/> const int maxn = 10001; <br/> const int INF = 0x7fffffff/2-1; <br/> typedef struct {int DIS, Vex;} elemtype; <br/> typedef struct {int Vex, DIS;} edge; <br/> typedef vector <edge> ve; <br/> ve edge [maxn]; <br/> bool CMP (elemtype E1, elemtype E2) <br/>{< br/> return e1.dis <e2.dis; <br/>}< br/> class hea P <br/>{< br/> Public: <br/> heap () {n = 0 ;}< br/> int min (INT _ A, int _ B) {<br/> return a [_ A]. dis <A [_ B]. dis? _ A: _ B; <br/>}< br/> void push (elemtype e) {<br/> for (I = ++ N; i> 1 & CMP (E, a [I> 1]); I >>= 1) {<br/> A [I] = A [I> 1]; <br/>}< br/> A [I] = E; <br/>}< br/> void POP () {<br/> elemtype E = A [n]; <br/> for (I = 2; I <N; I <= 1) {<br/> if (I <n-1) {<br/> I = min (I, I + 1 ); <br/>}< br/> If (CMP (E, a [I]) break; <br/> A [I> 1] = A [I]; <br/>}< br/> A [I> 1] = A [n --]; <br/>}< br/> elemtype top () {<br/> r Eturn A [1]; <br/>}< br/> bool empty () {<br/> return! N; <br/>}< br/> PRIVATE: <br/> elemtype A [maxn]; <br/> int N, I; <br/> }; <br/> void Dijkstra (INT nvex, int st) <br/>{< br/> heap h; <br/> edge e; <br/> elemtype TMP; <br/> int dis [maxn], I, now; <br/> bool visited [maxn] = {0}; </P> <p> TMP. dis = 0; <br/> TMP. vex = sT; <br/> H. push (TMP); <br/> for (I = 0; I <nvex; I ++) dis [I] = inf; <br/> dis [st] = 0; <br/> while (! H. empty () {<br/> TMP = H. top (); H. pop (); <br/> now = TMP. vex; <br/> If (! Visited [now]) {<br/> visited [now] = true; <br/> for (I = 0; I <(INT) edge [now]. size (); I ++) {<br/> E = edge [now] [I]; <br/> If (! Visited [E. vex] & dis [now] + E. dis <dis [E. vex]) {<br/> TMP. dis = dis [TMP. vex = E. vex] = dis [now] + E. DIS; <br/> H. push (TMP); <br/>}< br/> for (I = 0; I <nvex; I ++) {<br/> If (DIS [I] = inf) {<br/> printf ("-1 "); <br/>} else {<br/> printf ("% d", DIS [I]); <br/>}< br/> void _ test () <br/>{< br/> edge E; <br/> int n, m, I, A, B, C; </P> <p> scanf ("% d", & N, & M ); <br/> for (I = 0; I <n; I ++) {<br/> edge [I]. clear (); <br/>}< br/> for (I = 0; I <m; I ++) {<br/> scanf ("% d", & A, & B, & E. dis); <br/> E. vex = B; edge [A]. push_back (E); <br/> E. vex = A; edge [B]. push_back (E); <br/>}< br/> scanf ("% d", & A); <br/> Dijkstra (n, ); <br/>}< br/> int main () <br/>{< br/>__ test (); <br/>}< br/>/* <br/> 8 9 <br/> 0 1 5 <br/> 1 2 8 <br/> 1 3 7 <br /> 1 5 4 <br/> 4 5 6 <br/> 5 6 7 <br/> 6 7 3 <br/> 1 7 2 <br/> 1 6 1 <br/> 2 <br/> 3 3 <br/> 0 1 5 <br/> 0 2 1 <br/> 1 2 3 <br/> 0 <br/> 4 5 <br/> 0 1 1 <br/> 0 2 2 <br/> 0 3 5 <br/> 1 2 1 <br/> 1 3 2 <br /> */