OJ-Problems-Source/SDUTOJ/3562_jianrenfang.cpp

98 lines
1.9 KiB
C++

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <climits>
#include <cstring>
#include <string>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <vector>
#include <list>
#define mod 1000000007
#define inf 0x3f3f3f3f
#define pi acos(-1.0)
using namespace std;
typedef long long ll;
#define RANGE 1005
#define MAX 0x3f3f3f3f
int cost[RANGE][RANGE];
int d[RANGE];
bool used[RANGE];
int n,m;
int pre[1005];
void spfa(int s)
{
int i,j,now;
for(i=0;i<=n+1;i++)
{
d[i]=MAX;
used[i]=false;
}
int flag=0;
for(i=0;i<=n+1;i++)
{
if(cost[0][i]<MAX)pre[i]=i;//初始化pre数组
}
used[s]=true;
d[s]=0;
queue<int> q;
q.push(s);
while(!q.empty())
{
now=q.front();
q.pop();
for(i=0;i<=n+1;i++)
{
if(d[i]>d[now]+cost[now][i])
{
d[i]=d[now]+cost[now][i];
if(used[i]==0)
{
if(now!=0)pre[i]=pre[now];
used[i]==true;
q.push(i);
}
}
if(d[i]==d[now]+cost[now][i])
{
if(now!=0)pre[i]=min(pre[i],pre[now]);
}
}
}
}
int main()
{
int i,j,a,b,c;
int we;
scanf("%d",&we);
while(we--)
{scanf("%d%d",&n,&m);
if(!n&&!m) break;
for(i=0;i<=n+1;++i)
{
for(j=0;j<=i;j++)
{
if(i==j) cost[i][j]=0;
else cost[i][j]=cost[j][i]=MAX;
}
}
for(i=0;i<m;i++)
{
scanf("%d%d%d",&a,&b,&c);
cost[a][b]=c;
}
spfa(0);
if(d[n+1]<MAX)
{
if(pre[n+1]==n+1)printf("0\n");
else printf("%d\n",pre[n+1]);
}
else printf("-1\n");
}
return 0;
}