"Algorithmic Learning note" 63. BFS SJTU OJ 1281 Bounce

Typical BFS, find the starting point to search directly. It is important to note that the processing of layers. Coordinates-to-ID conversions. There is also the early judgment on whether to reach the end.

The code comment is very detailed, the last two functions are written at the beginning with the extraction adjacency matrix +dijkstra to calculate, very troublesome mind a hot result.

#include <vector>#include<queue>#include<iostream>using namespacestd;intmap[ to][ to]={0};intm,n,m1,m2;structpoint{intx; inty; intLay//The number of layers is used to calculate results}; Point S;//starting pointPoint e;//Endintgraph[ to* to][ to* to]={0};inlineintGetID (intXinty) {    if(X<=m and x>=1and y>=1and y<=N) {        if(map[x][y]!=0and map[x][y]!=2)//not water or swamp to return .            return(X-1) * N +y; }    return-1;} InlinevoidGetPoint (intIdint& X,int&y) {y= ID%N; if(y==0) y=N; X= ID/N;}voidinit () {cin>>M>>N>>M1>>M2;  for(inti =1; I <= M; ++i) { for(intj =1; J <= N; ++j) {cin>>Map[i][j]; if(map[i][j]==3) {s.x=i; S.y=J; }Else if(map[i][j]==4) {e.x=i; E.y=J; }        }    }}intBFs () {//Eight Directions    intdx[8] = {m1,m1,-m1,-m1,m2,m2,-m2,-M2}; intdy[8] = {m2,-m2,m2,-m2,m1,-m1,m1,-M1}; Queue<Point> Q;//the BFS queueS.lay =0;//indicates the number of layersQ.push (s); BOOLvis[ to* to] = {0}; intres=0;  while(!Q.empty ()) {Point cur=Q.front (); if(cur.x = = e.x and cur.y = = e.y)//In fact, this step is not necessary. Legacy of early Code             Break;        Q.pop (); Res=Cur.lay; Vis[getid (CUR.X,CUR.Y)]=true;//Access state Changes         for(inti =0; I <8; ++i) {intx = cur.x +Dx[i]; inty = cur.y +Dy[i]; intNEWID =GetID (x, y); if(newid!=-1and!Vis[newid])                {point P; P.x=x; P.Y=y; P.lay= Cur.lay +1; if(X==e.x and Y==e.y)//We found the end.                    returnP.lay;                Q.push (P); VIS[NEWID]=true;//Access state Changes            }        }    }        returnRes;}intMainintargcChar Const*argv[]) {        //Shortest Path Probleminit (); //Another method is to extract the adjacency matrix and then use the shortest path D algorithm//Buildadjmap (); //Cout<<dijkstra () <<endl;cout&LT;&LT;BFS () <<Endl; return 0;}voidBuildadjmap () {//Constructing adjacency matrices    intdx[8] = {m1,m1,-m1,-m1,m2,m2,-m2,-M2}; intdy[8] = {m2,-m2,m2,-m2,m1,-m1,m1,-M1};  for(inti =1; I <= M; ++i) {         for(intj=1; J <= N; ++j) {            intx, y; intFromid =GetID (I,J);  for(intK =0; K <8; ++K) {//Traverse 8 Directionsx = i +Dx[k]; Y= j +Dy[k]; intEndid =GetID (x, y); if(Endid! =-1) {Graph[fromid][endid]=1; Graph[endid][fromid]=1;//graph without Direction                }            }        }    }    }intDijkstra () {//Shortest Path algorithm It's too much trouble to write, it's mostly about trying to make    intres =0; intCNT = m*n;//total number of points    intBegin = GetID (s.x, S.Y);//starting point    intEnd = GetID (e.x, e.y);//End    Const intINF =9999999; intd[ to* to];//Storing temporary distances     for(inti =1; I <= CNT; ++i) d[i]= Graph[begin][i] >0?Graph[begin][i]: INF; D[begin]=0; ints[ to* to],q[ to* to];//doesn't Matter        intp_s=0, p_q=0, len_s =1, len_q = cnt-1 ; s[p_s++] =begin;  for(inti =1; I <= CNT; ++i)if(I! =begin) {Q[p_q++] =i; }         while(Len_q >1){        intu=0, mind =INF; intqid =0;  for(inti =0; i < p_q; ++i)if(q[i]!=0)        {            if(d[q[i]]<Mind ) {u=Q[i]; Mind=D[u]; QID=i; }        }        if(U = =0or U = =end) {             Break; } Q[qid]=0; len_q--; s[p_s+ +] = u; len_s++;  for(inti =0; i < p_q; ++i)if(q[i]!=0)        {            intv =Q[i]; if(Graph[u][v] >0){                if(D[v] > d[u]+Graph[u][v]) D[V]= D[u]+graph[u][v];//Update            }        }            }            returnd[end];}/*4 5 1 2 1 0 1 0 1 3 0 2 0 4 0 1 2 0 0 0 0 0 1 0 1-1 3-1 5 6-1 -1-1 10-1 12-1 -1-1 -1-1-1 19-1 */

"Algorithmic Learning note" 63. BFS SJTU OJ 1281 Bounce