POJ 3463 && HDU 1688 Sightseeing 次短路

#include <iostream>
#include <cstdio>
#include <queue>
using namespace std ;
const int maxn = 1010, maxm = 10010 ;
const int zhf = 1000000000 ;
inline void Read ( int &x ) { // 养成读入输出优化的习惯了。。。。
char c = getchar() ; bool f = 0 ; x = 0 ;
while ( !isdigit(c) ) {
if ( c == '-' ) f = 1 ;
c = getchar() ;
}
while ( isdigit(c) ) {
x = 10 * x + c - '0' ;
c = getchar() ;
} if (f) x = -x ;
}
inline void Print ( int x ) {
int len = 0 , s[20] = {0} ;
if ( x == 0 ) {
putchar('0') ;
return ;
} if ( x < 0 ) {
x = -x ;
putchar('-') ;
}
while (x) {
s[++len] = x % 10 ;
x /= 10 ;
}
while (len) putchar ( s[len--] + '0' ) ;
}
int to[maxm], e, n, m, be[maxn], nxt[maxm], w[maxm], d[maxn][2], cnt[maxn][2] ;
bool vis[maxn][2] ;
//后面的[2]，[0]表示最短路中，[1]表示次短路中
void add ( int x, int y, int z ) {
to[++e] = y ;
nxt[e] = be[x] ;
be[x] = e ;
w[e] = z ;
}//链式前向星
void init() {
int i ;
e = 0 ;
for ( i = 0 ; i < maxn ; i ++ )
to[i] = be[i] = nxt[i] = w[i] = vis[i][0] = vis[i][1] = cnt[i][1] = cnt[i][0] = 0,
d[i][1] = d[i][0] = zhf ;
for ( i = maxn ; i < maxm ; i ++ )
to[i] = nxt[i] = w[i] = 0 ;
}//初始化
int dijkstra ( int st, int end ) {
int i, j, k ; // Kind
d[st][0] = 0 ; cnt[st][0] = 1 ;
for ( i = 1 ; i <= n << 1 ; i ++ ) {
int minn = zhf , u = -1 ;
for ( j = 1 ; j <= n ; j ++ )
for ( int flag = 0 ; flag <= 1 ; flag ++ )
if ( !vis[j][flag] && d[j][flag] < minn ) {
u = j ;
minn = d[j][flag] ;
k = flag ;
}
if ( u == -1 ) break ;
vis[u][k] = 1 ;
for ( j = be[u] ; j ; j = nxt[j] ) {
int v = to[j] ;
int wei = d[u][k] + w[j] ;
if ( wei < d[v][0] ) { // 更新最短路
d[v][1] = d[v][0] ;
cnt[v][1] = cnt[v][0] ;
d[v][0] = wei ;
cnt[v][0] = cnt[u][k] ;
} else if ( wei == d[v][0] ) { //等于最短路
cnt[v][0] += cnt[u][k] ;
} else if ( wei < d[v][1] ) { //更新次短路
d[v][1] = wei ;
cnt[v][1] = cnt[u][k] ;
} else if ( wei == d[v][1] ) //等于次短路
cnt[v][1] += cnt[u][k] ;
}
}
int res = cnt[end][0] ;
if ( d[end][1] - 1 == d[end][0] ) //是否需要加入次短路数量
res += cnt[end][1] ;
return res ;
}
int main () {
int i, j, k, st, end, x, y, z, t ;
Read(t) ;
while ( t -- ) {
init() ;
Read(n) ; Read(m) ;
for ( i = 1 ; i <= m ; i ++ ) {
Read(x) ; Read(y) ; Read(z) ;
add ( x, y, z ) ; //有向图
} Read(st) ; Read (end) ;
Print ( dijkstra( st, end ) ) ;
putchar('\n');
}
return 0 ;
}