MPI Maelstrom POJ - 1502 floyd

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<iostream>
using namespace std;
const int N=110;
const int INF = 0x3f3f3f3f;
char s[20];
int n;
int f[N][N];
void init()
{
    for(int i = 1 ; i <=  n ; i++)
        for(int j = 1; j <= n ; j++)
            if(i == j)
                f[i][j] = 0;
            else
                f[i][j] = INF ;
            
}
void floyd()
{
    for(int k = 1; k <= n ; k++)
        for(int i = 1; i <= n ; i++)
            for(int j = 1; j <= n ; j++)
                f[i][j] = min(f[i][j],f[i][k] +f[k][j]);
    int ans = -INF ;
    for(int i = 1; i <= n ; i++)
        if(f[1][i] !=INF)
            ans = max(ans,f[1][i]);
    cout<<ans<<endl;
}
int main()
{
    cin>>n;
    init();
    for(int i = 2; i <= n ; i++)
        for(int j = 1; j < i; j++)
        {
            cin>>s;
            if(s[0]!= 'x')
            {
                int num = atoi(s);
                f[i][j] = f[j][i] = num;
            }
        }
    floyd();
    return 0;
}