hdu 2112(最短路+hash+二分)

/*
  Name: 最短路(dijkstra邻接矩阵)+hash判重并统计顶点数+二分查找返回顶点位置 
  Copyright: 
  Author: Try_86
  Date: 12/04/12 20:57
  Description: 注意：起始点和终点不在给出的路线中的情况！！！ 
*/
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>

using namespace std;

const int S = 163; 
const int N = 155;
const int M = 12000;
const int MAX = 1000000000; 

char names[N][35], sName[35], eName[35];
int dis[N], sumVs;
struct edge {
    char u[35];
    char v[35];
    int w;
}e[M];
bool vis[N];
int map[N][N];

struct node {//hash表相关数据信息 
    char str[35];
    node *next;
    node(char *ch, node *p) {
        strcpy(str, ch);
        next = p;
    }
};
struct hash {
    node *link;
}hashTable[S];

void initHashTable() {//hash表初始化 
    for (int i=0; i<S; ++i) hashTable[i].link = NULL;
    return ;
}

unsigned int BKDRHash(char *str) {//hash
    unsigned int seed = 131;
    unsigned int hash = 0;
    while (*str) hash = hash * seed + (*str++);
    return hash & 0x7FFFFFFF;
}

void insertAndFind(char *str) {//hash表中插入与查找 
    int k = BKDRHash(str) % S;
    node *p = hashTable[k].link;
    while (p) {
        if (!strcmp(p->str, str)) return ;
        p = p->next;
    }
    node *q = new node(str, NULL);
    q->next = hashTable[k].link;
    hashTable[k].link = q;
    strcpy(names[sumVs++], str);
    return ;
}

void del(node *p) {//释放哈希表所占内存 
    if (!p) return ;
    del(p->next);
    delete p;
}

int cmp(const void *a, const void *b) {
    return (strcmp((char *)a, (char *)b));
}

int binarySearch(char *str) {//二分查找定位顶点位置 
    int left = 0;
    int right = sumVs;
    while (left <= right) {
        int mid = (left + right) / 2;
        if (!strcmp(names[mid], str)) return mid;
        if (strcmp(names[mid], str) > 0) right = mid - 1;
        else left = mid + 1;
    }
    return -1;//起始点或终点不在二分查找表中是返回-1 
}

void init(int vs) {//邻接矩阵初始化 
    for (int i=0; i<vs-1; ++i) {
        map[i][i] = 0;
        for (int j=i+1; j<vs; ++j)    map[i][j] = map[j][i] = MAX;
    }
    return ;
}

void dijkstra(int vs, int s) {//最短路 
    memset(vis, false, sizeof(vis));
    int pos = s;
    vis[pos] = true;
    for (int i=0; i<vs; ++i) dis[i] = map[pos][i];
    dis[pos] = 0;
    int minLen;
    for (int i=1; i<vs; ++i) {
        pos = s;
        minLen = MAX;
        for (int j=0; j<vs; ++j) {
            if (!vis[j] && minLen>dis[j]) minLen = dis[j], pos = j;
        } 
        vis[pos] = true;
        for (int j=0; j<vs; ++j) {
            int len = dis[pos] + map[pos][j];
            if (!vis[j] && dis[j]>len) dis[j] = len;    
        }
    }
    return ;
}

int main() {
    int n;
    while (scanf("%d", &n), n!=-1) {
        scanf ("%s%s", sName, eName);
        sumVs = 0;
        initHashTable();
        for (int i=0; i<n; ++i) {
            scanf ("%s%s%d", e[i].u, e[i].v, &e[i].w);
            insertAndFind(e[i].u); //插入hash表 
            insertAndFind(e[i].v); //插入hash表 
        }
        qsort(names, sumVs, sizeof(names[0]), cmp);
        init(sumVs);
        for (int i=0; i<n; ++i) {
            int u = binarySearch(e[i].u); //对每条线路的起始点和终点返回顶点位置 
            int v = binarySearch(e[i].v); 
            if (map[u][v] > e[i].w) map[u][v] = map[v][u] = e[i].w;//判重，选最小者 
        }
        int s = binarySearch(sName);
        int t = binarySearch(eName);
        if (s==-1 || t==-1) {//起点或终点不在二分查找表中 
            printf ("-1\n");
            continue;
        }
        dijkstra(sumVs, s);
        if (dis[t] == MAX) printf ("-1\n");
        else printf ("%d\n", dis[t]);
        for (int i=0; i<S; ++i) del(hashTable[i].link);
    }
    return 0;
}

 

转载于:https://www.cnblogs.com/try86/archive/2012/04/12/2444709.html