poj1502

最短路

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

#define inf 0x3f3f3f3f
#define maxn 105

int vis[maxn];
int cost[maxn][maxn];
int lowcost[maxn];
int n;

void dijkstra(int beg)
{
    int i, j, min;
    memset(vis, 0, sizeof(vis));
    vis[beg] = 1;
    for (i = 0; i < n; i++)
        lowcost[i] = cost[beg][i];
    lowcost[beg] = 0;
    int pre = beg;
    for (i = 1; i < n; i++)
    {
        min = inf;
        for (j = 0; j < n; j++)
            if (vis[j] == 0 && lowcost[pre] + cost[pre][j] < lowcost[j])
                lowcost[j] = lowcost[pre] + cost[pre][j];
        for (j = 0; j < n; j++)
            if (vis[j] == 0 && lowcost[j] < min)
            {
                min = lowcost[j];
                pre = j;
            }
        vis[pre] = 1;
    }
}

void input()
{
    char st[100];
    for (int i = 1; i < n; i++)
        for (int j = 0; j < i; j++)
        {
            scanf("%s", st);
            if (st[0] == 'x')
                cost[i][j] = cost[j][i] = inf;
            else
                cost[i][j] = cost[j][i] = atoi(st);
        }
}

int main()
{
    //freopen("t.txt", "r", stdin);
    scanf("%d", &n);
    input();
    dijkstra(0);
    int ans = 0;
    for (int i = 0; i < n; i++)
        ans = max(ans, lowcost[i]);
    printf("%d\n", ans);
    return 0;
}