思维题(转换) HDU 4370 0 or 1

#include <bits/stdc++.h>
using namespace std;

const int N = 3e2 + 5;
const int INF = 0x3f3f3f3f;
int w

;
int d
;
bool vis
;
int n;

void SPFA(int s)	{
memset (vis, false, sizeof (vis));
queue<int> que;
for (int i=1; i<=n; ++i)	{
if (i == s)	d[s] = INF;
else	{
d[i] = w[s][i];
vis[i] = true;
que.push (i);
}
}
while (!que.empty ())	{
int u = que.front ();	que.pop ();
vis[u] = false;
for (int i=1; i<=n; ++i)	{
if (d[i] > d[u] + w[u][i])	{
d[i] = d[u] + w[u][i];
if (!vis[i])	{
vis[i] = true;	que.push (i);
}
}
}
}
}

int main(void)	{
while (scanf ("%d", &n) == 1)	{
for (int i=1; i<=n; ++i)	{
for (int j=1; j<=n; ++j)	{
scanf ("%d", &w[i][j]);
}
}
SPFA (1);
int ans = d
;
int a1 = d[1];
SPFA (n);
int a2 = d
;
printf ("%d\n", min (ans, a1 + a2));
}

return 0;
}