Dijkstra 算法
/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
Copyright (c) 2011 panyanyany All rights reserved.
URL : http://acm.hdu.edu.cn/showproblem.php?pid=1596
Name : 1596 find the safest road
Date : Sunday, January 22, 2012
Time Stage : half an hour
Result:
5286524 2012-01-22 16:22:38 Accepted 1596
1015MS 6632K 1962 B
C++ pyy
Test Data :
Review :
//----------------------------------------------------------------------------*/
#include
#include
#include
#include
#include
#include
using namespace std ; #define INF (-1) #define MAXN 1002 typedef __int64 LL ; #define min(x, y) ((x) < (y) ? (x) : (y)) #define max(x, y) ((x) > (y) ? (x) : (y)) #define MEM(a, v) memset (a, v, sizeof (a)) bool used[MAXN] ; int n, q ; double map[MAXN][MAXN], dist[MAXN] ; double dijkstra (const int beg, const int end) { int i, j ; int iMinPath ; double MaxSafe ; MEM (used, 0) ; for (i = 1 ; i <= n ; ++i) dist[i] = map[beg][i] ; for (i = 1 ; i <= n ; ++i) { iMinPath = 1 ; MaxSafe = 0 ; for (j = 1 ; j <= n ; ++j) { if (used[j] || dist[j] == 0) continue ; if (dist[j] > MaxSafe) { iMinPath = j ; MaxSafe = dist[j] ; } } used[iMinPath] = 1 ; for (j = 1 ; j <= n ; ++j) { if (used[j] || dist[iMinPath] == 0 || map[iMinPath][j] == 0) continue ; if (dist[j] == 0 || dist[j] < dist[iMinPath] * map[iMinPath][j]) dist[j] = dist[iMinPath] * map[iMinPath][j] ; } } return dist[end] ; } int main () { int i, j ; int x, y ; double ret ; while (~scanf ("%d", &n)) { for (i = 1 ; i <= n ; ++i) for (j = 1 ; j <= n ; ++j) { scanf ("%lf", &map[i][j]) ; } scanf ("%d", &q) ; for (i = 1 ; i <= q ; ++i) { scanf ("%d%d", &x, &y) ; ret = dijkstra (x, y) ; if (ret == 0) puts ("What a pity!") ; else printf ("%.3lf\n", ret) ; } } return 0 ; }
Floyd 算法
/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
Copyright (c) 2011 panyanyany All rights reserved.
URL : http://acm.hdu.edu.cn/showproblem.php?pid=1596
Name : 1596 find the safest road
Date : Sunday, January 22, 2012
Time Stage : half an hour
Result:
5286856 2012-01-22 19:02:13 Accepted 1596
3484MS 6620K 1456 B
C++ pyy
Test Data :
Review :
//----------------------------------------------------------------------------*/
#include
#include
#include
#include
#include
#include
#include
using namespace std ;
#define INF (-1)
#define MAXN 1002
typedef __int64 LL ;
#define min(x, y) ((x) < (y) ? (x) : (y))
#define max(x, y) ((x) > (y) ? (x) : (y))
#define MEM(a, v) memset (a, v, sizeof (a))
int n, q ;
double map[MAXN][MAXN] ;
void floyd ()
{
int i, j, k ;
double d ;
for (k = 1 ; k <= n ; ++k)
for (i = 1 ; i <= n ; ++i)
for (j = 1 ; j <= n ; ++j)
{
// 像这种数据这么大的题（n<=1000），加多条判断语句都会超时……
// 之前这里就是加了一条判断，结果就超时了……无限TLE
d = map[i][k] * map[k][j] ;
if (map[i][j] < d)
map[i][j] = d ;
}
}
int main ()
{
int i, j ;
int x, y ;
double ret ;
while (~scanf ("%d", &n))
{
for (i = 1 ; i <= n ; ++i)
for (j = 1 ; j <= n ; ++j)
{
scanf ("%lf", &map[i][j]) ;
}
floyd () ;
scanf ("%d", &q) ;
for (i = 1 ; i <= q ; ++i)
{
scanf ("%d%d", &x, &y) ;
ret = map[x][y] ;
if (ret == 0)
puts ("What a pity!") ;
else
printf ("%.3lf\n", ret) ;
}
}
return 0 ;
}
Spfa 算法
/* THE PROGRAM IS MADE BY PYY */
/*----------------------------------------------------------------------------//
Copyright (c) 2011 panyanyany All rights reserved.
URL :
Name :
Date :
Time Stage :
Result:
5287003 2012-01-22 21:15:06 Accepted 1596
1046MS 6656K 1783 B
C++ pyy
Test Data :
Review :
//----------------------------------------------------------------------------*/
#include
#include
#include
#include
#include
#include
#include
using namespace std ; #define INF (-1) #define MAXN 1002 typedef __int64 LL ; #define min(x, y) ((x) < (y) ? (x) : (y)) #define max(x, y) ((x) > (y) ? (x) : (y)) #define MEM(a, v) memset (a, v, sizeof (a)) bool used[MAXN] ; int n, q ; double map[MAXN][MAXN], dist[MAXN] ; double spfa (const int beg, const int end) { int i, t ; double d ; queue
q ; MEM (used, 0) ; MEM (dist, 0) ; q.push (beg) ; used[beg] = 1 ; dist[beg] = 1 ; // 记得要初始化出发点为1 while (!q.empty ()) { t = q.front () ; q.pop () ; for (i = 1 ; i <= n ; ++i) { d = dist[t] * map[t][i] ; if (dist[i] < d) { dist[i] = d ; if (!used[i]) { q.push (i) ; used[i] = 1 ; // 第一次忘了这个，死循环 } } } used[t] = 0 ; } return dist[end] ; } int main () { int i, j ; int x, y ; double ret ; while (~scanf ("%d", &n)) { for (i = 1 ; i <= n ; ++i) for (j = 1 ; j <= n ; ++j) { scanf ("%lf", &map[i][j]) ; } scanf ("%d", &q) ; for (i = 1 ; i <= q ; ++i) { scanf ("%d%d", &x, &y) ; ret = spfa (x, y) ; if (ret == 0) puts ("What a pity!") ; else printf ("%.3lf\n", ret) ; } } return 0 ; }
