学步园

最直接的最小生成树，不解释了。

代码如下：

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

int N, pos, set[105];

struct Node
{
    int x, y, dist;
    bool operator < (Node t) const 
    {
        return dist < t.dist;
    }
}e[10005];

int find(int x)
{
    return set[x] = x == set[x] ? x : find(set[x]);
}

void merge(int a, int b)
{
    set[a] = b;
}

int main()
{
    int c, cnt, ans;
    while(scanf("%d", &N) == 1) { 
        pos = cnt = ans = 0;
        for (int i = 1; i <= N; ++i) {
            set[i] = i;
            for (int j = 1; j <= N; ++j) {
                scanf("%d", &c);
                ++pos;
                e[pos].x = i, e[pos].y = j, e[pos].dist = c;
            }
        }  
        sort(e+1, e+1+pos);
        for (int i = 1; i <= pos; ++i) {
            int a = find(e[i].x), b = find(e[i].y);
            if (a != b) {
                merge(a, b);
                ans += e[i].dist;
                ++cnt;
                if (cnt == N-1) {
                    break;
                }
            }
        }
        printf("%d\n", ans);
    }
    return 0;
}