北大校赛2011 Word Ladder(C题) 解题报告

套用模板，进行广搜。

#include <iostream>#include <cstring>#include <cstdio>#include <queue>using namespace std;#define INFINITY 0#define MAX_VERTEX_NUM 6001  //顶点最多个数#define LENGTH 20           //顶点字符长度//*********************************邻接表***********************************begintypedef char VertexType[LENGTH];typedef struct ArcNode{    int adjvex;    struct ArcNode* nextarc;    int weight;}ArcNode;typedef struct VNode{    VertexType data;    ArcNode *firstarc;}VNode, AdjList[MAX_VERTEX_NUM];typedef struct{    AdjList vertices;    int vexnum;    int arcnum;}ALGraph;int Judge(char *s1,char *s2){int n1=strlen(s1);int n2=strlen(s2);if(n1!=n2) return 0;int count=0;for(int i=0;i<n1;i++){if(s1[i]!=s2[i]) count++;}return count==1 ? 1 : 0;}int LocateVex(const ALGraph & g, char name[LENGTH]){    for (int i = 0; i < g.vexnum; i++)        if (0 == strcmp(g.vertices[i].data, name))            return i;    return -1;}//图的建造void CreateGraph(ALGraph &g){    int i=0;while(cin>>g.vertices[i].data){        g.vertices[i].firstarc = NULL;        i++;    }    g.vexnum=i;    ArcNode *p, *q;    ArcNode *pTmp;    g.arcnum=0;    for (int i = 0; i < g.vexnum; i++){    for(int j = i+1;j < g.vexnum;j++){    if(Judge(g.vertices[i].data,g.vertices[j].data)){    g.arcnum++;    int x = i;            int y = j;            p = new ArcNode;        q = new ArcNode;        p->adjvex = y;        p->nextarc = NULL;        p->weight = 1;        q->adjvex = x;        q->nextarc = NULL;        q->weight = 1;        if (NULL == g.vertices[x].firstarc)            g.vertices[x].firstarc = p;        else{            for (pTmp = g.vertices[x].firstarc; NULL != pTmp->nextarc; pTmp = pTmp->nextarc);            pTmp->nextarc = p;        }        if (NULL == g.vertices[y].firstarc)            g.vertices[y].firstarc = q;        else{            for (pTmp = g.vertices[y].firstarc; NULL != pTmp->nextarc; pTmp = pTmp->nextarc);            pTmp->nextarc = q;        }    }        }    }}//v的第一个邻接点int FirstAdjVex(const ALGraph &g, int v){    if ( NULL != g.vertices[v].firstarc)        return g.vertices[v].firstarc->adjvex;    return -1;}//v相对于w的下一个邻接点int NextAdjVex(const ALGraph &g, int v, int w){    ArcNode *p;    for (p = g.vertices[v].firstarc; NULL != p; p = p->nextarc)        if (p->adjvex == w && p->nextarc != NULL)            return p->nextarc->adjvex;    return -1;}//*********************************邻接表***********************************endbool visit[MAX_VERTEX_NUM];//广度优先遍历int pre[MAX_VERTEX_NUM];void BFSTraverse(ALGraph &g, char vName1[LENGTH],char vName2[LENGTH]){memset(pre,-1,sizeof(pre));    int pos = LocateVex(g, vName1);    for (int v = 0; v < g.vexnum; v++)        visit[v] = false;    queue<int> q;    if (!visit[pos]){        pre[pos]=-1;//cout<<g.vertices[pos].data<<'\t';//访问         visit[pos] = true;    }    q.push(pos);        int v,w;    while (!q.empty()){        v = q.front();        q.pop();        for (w = FirstAdjVex(g, v); w >= 0; w = NextAdjVex(g, v, w)){            if (!visit[w]){                //cout<<g.vertices[w].data<<'\t';//访问                 pre[w]=v;visit[w] = true;if(strcmp(g.vertices[w].data,vName2)==0) break;                q.push(w);            }        }        if(strcmp(g.vertices[w].data,vName2)==0) break;    }    //cout<<endl;}/******************************题目相关****************************************/ int Count(int pre[],int n){int i,count=0;for(i=n;i!=-1;i=pre[i]) count++;return count;}int main(){//freopen("input.txt","r",stdin);     ALGraph graph;    CreateGraph(graph);BFSTraverse(graph, graph.vertices[0].data,graph.vertices[1].data);cout<<Count(pre,1)<<endl;    return 0;}