poj-2421 Constructing Roads *

/*
 * 蛮水的一道MST  Kruskal， 链表实现
 *
 * 预处理：
 *     根据已有的边，把相应的集合合并。。再Kruskal
 *
 * 另一种方法：
 *     把已有边的权值改为0
 *
 */
#include <cstdio>
#include <algorithm>
using namespace std;

const int maxN = 100 + 5;
int n, totEdgeNum, G[maxN][maxN], q, ans;

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

struct SNode{
    int num, len;
    SNode *rep, *next;
};
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;
    x->len = 1;

    return x;
}
SNode* findSet(SNode *x){
    return x->rep;
}
SNode* unionSet(SNode *lhs, SNode *rhs){
    SNode *first, *second, *cur;
    if(lhs->rep->len >= rhs->rep->len){
        first = lhs->rep; second = rhs->rep;
    }
    else{
        first = rhs->rep; second = lhs->rep;
    }

    cur = second;
    while(cur != NULL){
        cur->rep = first;
        cur = cur->next;
    }
    tail[first->num]->next = head[second->num];
    tail[first->num] = tail[second->num];
    head[second->num] = head[first->num];

    return first;
}

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

void mstKruskal(){
    qsort(edge, totEdgeNum, sizeof(SEdge), cmp);

/*
    for(int i=0; i<totEdgeNum; i++){
        printf("%d ", edge[i].w);
    }
    printf("\n");
*/


    for(int i=0; i<totEdgeNum; i++){
        if(findSet(node[edge[i].u]) != findSet(node[edge[i].v])){
            ans += edge[i].w;
            unionSet(node[edge[i].u], node[edge[i].v]);
        }
    }
}




int main(){
    //图输入
    scanf("%d", &n);
    for(int i=0; i<n; i++){
        for(int j=0; j<n; j++){
            scanf("%d", &G[i][j]);
        }
    }

    totEdgeNum = 0;
    for(int i=0; i<n; i++){
        for(int j=0; j<=i; j++){
            edge[totEdgeNum].u = i;
            edge[totEdgeNum].v = j;
            edge[totEdgeNum].w = G[i][j];
            totEdgeNum++;
        }
    }


    //初始化
    for(int i=0; i<n; i++){
        node[i] = new SNode;
        node[i]->num = i;
        makeSet(node[i]);
    }
    scanf("%d", &q);
    int u, v;
    for(int i=0; i<q; i++){
        scanf("%d%d", &u, &v);
        if(node[u-1]->rep != node[v-1]->rep)
            unionSet(node[u-1], node[v-1]);
    }


    //kruskal
    mstKruskal();

    printf("%d\n", ans);


    return 0;
}