Poj2240arbitrage determines whether a negative ring exists

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/*

Question:

Ask if I can make a profit after a round trip

Analysis:

Whether the directed graph is in a negative ring, because each vertex may have a negative ring,

Directly use flordAlgorithmJust do it.

*/

# Include <iostream>

# Include <string>

# Include <cstring>

Using namespace STD;

# Define x 35

String City [X], S1, S2;

Double map [x] [x];

Int main ()

{

Freopen ("sum. In", "r", stdin );

Freopen ("sum. Out", "W", stdout );

Int m, n, x, y, CNT = 0;

Double DIS;

While (CIN> N, N)

{

Memset (MAP, 0, sizeof (MAP ));

For (INT I = 0; I <n; I ++)

{

Cin> City [I];

Map [I] [I] = 1;

}

Cin> m;

For (INT I = 0; I <m; I ++)

{

Cin> S1> dis> S2;

For (Int J = 0; j <n; j ++) // locate the start point and end point.

{

If (S1 = City [J])

X = J;

If (s2 = City [J])

Y = J;

}

Map [x] [Y] = DIS; // path length of the Directed Graph

}

For (int K = 0; k <n; k ++) // fload Algorithm

For (INT I = 0; I <n; I ++)

For (Int J = 0; j <n; j ++)

If (Map [I] [J] <map [I] [k] * map [k] [J]) // relaxation operation

Map [I] [J] = map [I] [k] * map [k] [J];

Bool flag = true;

For (INT I = 0; I <n; I ++)

If (Map [I] [I]> 1) // if a negative ring exists

Flag = false;

If (! Flag)

Printf ("case % d: Yes \ n", ++ CNT );

Else

Printf ("case % d: NO \ n", ++ CNT );

}

Return 0;

}