hdu 1142 最短路+记忆化搜索

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

const int INF = 99999999;
const int N = 1001;
const int M = N * N;
int head
;
int dist
;
int dp
;
bool visit
;
int n, m, e;

struct Edge
{
int v, next, w;
} edge[M];

void addEdge( int u, int v, int w )
{
edge[e].v = v;
edge[e].w = w;
edge[e].next = head[u];
head[u] = e++;
}

void dij( int s )
{
memset( visit, false, sizeof(visit) );
for ( int i = 0; i <= n; i++ )
{
dist[i] = INF;
}
dist[s] = 0;
for ( int i = 1; i <= n; i++ )
{
int u = 0;
for ( int j = 1; j <= n; j++ )
{
if ( !visit[j] && dist[j] < dist[u] )
{
u = j;
}
}
visit[u] = true;
for ( int j = head[u]; j != -1; j = edge[j].next )
{
int v = edge[j].v, w = edge[j].w;
if ( !visit[v] && dist[u] + w < dist[v] )
{
dist[v] = dist[u] + w;
}
}
}
}

int dfs( int u )
{
if ( dp[u] ) return dp[u];
int sum = 0;
for ( int i = head[u]; i != -1; i = edge[i].next )
{
int v = edge[i].v;
if ( dist[u] > dist[v] )
{
sum += dfs(v);
}
}
return dp[u] = sum;
}

int main ()
{
while ( scanf("%d", &n), n )
{
e = 0;
memset( head, -1, sizeof(head) );
scanf("%d", &m);
while ( m-- )
{
int u, v, w;
scanf("%d%d%d", &u, &v, &w);
addEdge( u, v, w );
addEdge( v, u, w );
}
dij(2);
memset( dp, 0, sizeof(dp) );
dp[2] = 1;
int ans = dfs(1);
printf("%d\n", ans);
}
return 0;
}