poj-1789 Truck History *

/*
 * 很直接的最小生成树
 *
 * 版本一： Kruskal， 链表实现
 *
 */

#include <cstdio>
#include <algorithm>
using namespace std;

const int maxN = 2000 + 5;
const int letterNum = 7;
int n, totEdgeNum, ans;
char code[maxN][letterNum + 2];

struct SEdge{            //边
    int w, u, v;
};
SEdge edge[maxN * maxN];

struct SNode{            //链表的节点
    SNode *rep, *next;
    int num;
};
SNode *head[maxN], *tail[maxN], *node[maxN];

SNode *makeSet(SNode *x){
    head[x->num] = x;
    tail[x->num] = x;
    x->rep = x; x->next = NULL;

    return x;
}
SNode *findSet(SNode *x){
    return x->rep;
}
//直接把 rhs 连在 lhs 后面
SNode *unionSet(SNode *lhs, SNode *rhs){
    SNode *lhsRep = findSet(lhs);
    SNode *rhsRep = findSet(rhs);

    tail[lhsRep->num]->next = rhsRep;
    SNode *tmpNode = rhsRep;
    while(tmpNode != NULL){
        tmpNode->rep = lhsRep;
        tmpNode = tmpNode->next;
    }

    tail[lhsRep->num] = tail[rhsRep->num];
    head[rhsRep->num] = head[lhsRep->num];

    return lhsRep;
}

int cmp(const void *lhs, const void *rhs){
    SEdge *a = (SEdge *)lhs; SEdge *b = (SEdge *)rhs;
    return a->w - b->w;
}

void mstKruskal(){
    //初始化
    for(int i=0; i<n; i++){
        node[i] = new SNode;
        node[i]->num = i;
        makeSet(node[i]);
    }
    //边按权值排序
    qsort(edge, totEdgeNum, sizeof(SEdge), cmp);

    for(int i=0; i<totEdgeNum; i++){
        SNode *uRep = findSet(node[edge[i].u]);
        SNode *vRep = findSet(node[edge[i].v]);

        if(uRep != vRep){
            unionSet(uRep, vRep);
            ans += edge[i].w;
        }
    }

}

//计算边的权值
int inline getDistance(char *lhs, char *rhs){
    int dis = 0;
    for(int i=0; i<letterNum; i++)
        if(lhs[i] != rhs[i]) dis++;
    return dis;
}


int main(){
    while(scanf("%d", &n)){
        if(n == 0) return 0;

        ans = totEdgeNum = 0;
        getchar();
        for(int i=0; i<n; i++){
            gets(code[i]);
            for(int j=0; j<=i; j++){
                edge[totEdgeNum].w = getDistance(code[i], code[j]);
                edge[totEdgeNum].u = i; edge[totEdgeNum].v = j;
                totEdgeNum++;
            }
        }

        mstKruskal();

        printf("The highest possible quality is 1/%d.\n", ans);

    }



    return 0;
}

--

/*
 * 很直接的最小生成树
 *
 * 版本二： Kruskal， 不相交集合森林
 *
 */

#include <cstdio>
#include <algorithm>
using namespace std;

const int maxN = 2000 + 5;
const int letterNum = 7;
int n, totEdgeNum, ans;
char code[maxN][letterNum + 2];

struct SEdge{            //边
    int w, u, v;
};
SEdge edge[maxN * maxN];

struct SNode{            //链表的节点
    SNode *p;
    int num, rank;
};
SNode *node[maxN];

SNode *makeSet(SNode *x){
    x->p = x;
    x->rank = 0;

    return x;
}
SNode *findSet(SNode *x){
    if(x != x->p)
        x->p = findSet(x->p);    //路径压缩
    return x->p;
}
void link(SNode *lhs, SNode *rhs){
    if(lhs->rank > rhs->rank)    //按秩合并
        rhs->p = lhs;
    else{
        lhs->p = rhs;
        if(lhs->rank == rhs->rank)
            rhs->rank++;
    }
}
void unionSet(SNode *lhs, SNode *rhs){
    link(findSet(lhs), findSet(rhs));
}


int cmp(const void *lhs, const void *rhs){
    SEdge *a = (SEdge *)lhs; SEdge *b = (SEdge *)rhs;
    return a->w - b->w;
}

void mstKruskal(){
    //初始化
    for(int i=0; i<n; i++){
        node[i] = new SNode;
        node[i]->num = i;
        makeSet(node[i]);
    }
    //边按权值排序
    qsort(edge, totEdgeNum, sizeof(SEdge), cmp);

    for(int i=0; i<totEdgeNum; i++){
        SNode *uRep = findSet(node[edge[i].u]);
        SNode *vRep = findSet(node[edge[i].v]);

        if(uRep != vRep){
            unionSet(uRep, vRep);
            ans += edge[i].w;
        }
    }

}

//计算边的权值
int inline getDistance(char *lhs, char *rhs){
    int dis = 0;
    for(int i=0; i<letterNum; i++)
        if(lhs[i] != rhs[i]) dis++;
    return dis;
}


int main(){
    while(scanf("%d", &n)){
        if(n == 0) return 0;

        ans = totEdgeNum = 0;
        getchar();
        for(int i=0; i<n; i++){
            gets(code[i]);
            for(int j=0; j<=i; j++){
                edge[totEdgeNum].w = getDistance(code[i], code[j]);
                edge[totEdgeNum].u = i; edge[totEdgeNum].v = j;
                totEdgeNum++;
            }
        }

        mstKruskal();

        printf("The highest possible quality is 1/%d.\n", ans);

    }



    return 0;
}