图论笔记√

首先最简单的存图方式：邻接矩阵

mp[i][j]表示从i->j有一条边权为mp[i][j]的边//如果是无限大的话就是算作没有边

e.g.http://218.5.5.242:9018/JudgeOnline/problem.php?id=1144

这里mp[xx][yy]=（xx和yy的距离）

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define inf 2000022800.00
using namespace std;
int n,m;
double x[105],y[105];
double a[105][105];
double mp[105][105];

double MIN(double x,double y)
{
    if(x>y)return y;
    else return x;
}
int main()
{
    scanf("%d",&n);
//    memset(mp,127/3,sizeof(mp));

    for(int i=1;i<=n;++i)for(int j=1;j<=n;++j)mp[i][j]=inf;
    for(int i=1;i<=n;++i)
    {
        mp[i][i]=0;
        scanf("%lf%lf",&x[i],&y[i]);
    }
    cin>>m;
    for(int i=1;i<=m;++i)
    {
        int xx,yy;
        scanf("%d%d",&xx,&yy);
        mp[xx][yy]=sqrt((x[xx]-x[yy])*(x[xx]-x[yy])+(y[xx]-y[yy])*(y[xx]-y[yy]));
    }
    int xx,yy;
    cin>>xx>>yy;
    for(int k=1;k<=n;++k)
    {
        for(int i=1;i<=n;++i)
        {
            for(int j=1;j<=n;++j)
            {
                mp[i][j]=MIN(mp[i][j],mp[i][k]+mp[k][j]);
            }
        }
    }
    printf("%.2lf",mp[xx][yy]);
    puts("");

    return 0;
}