解 （a）图中有1条前向通路，4个回路
P1?G1G2G3G4，?1?1L1?G2G3H1
L2??G1G2G3H3，L3?G1G2G3G4H4，L4??G3G4H2，??1?(L1?L2?L3?L4)则有
G1G2G3G4?C(s)P ?11?R(s)?1?G2G3H1?G1G2G3H3?G1G2G3G4H4?G3G4H2 P，P2?G3G4，?2?1?L1?1?G1H1，1?G1G2G3，?1?1 L1??G1H1，L2?G3H3，L3??G1G2G3H1H2H3， ??1?(L1?L2?L3)?L1L2，（b）图中有2条前向通路，3个回路，有1对互不接触回路
则有
G1G2G3?G3G4(1?G1H1)??P2?2C(s)P ?11?R(s)?1?G1H1?G3H3?G1G2G3H1H2H3?G1H1G3H3（c）图中有4条前向通路，5个回路
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P1??G1，P2?G1G2，P3?G2，P4?G2G1， L1?G1，L2??G1G2，L3??G2，L4??G2G1，L5??G1G2， ?1??2??3??4?1，??1?(L1?L2?L3?L4)，则有
C(s)P1?1?P2?2?P3?3?P4?4 ?R(s)???G1?G1G2?G2?G2G12G1G2?G1?G2 ?1?G1?G1G2?G2?G2G1?G1G21?G1?G2?3G1G2
（d）图中有2条前向通路，5个回路
P，P2?G3，?2?1，1?G1G2，?1?1 则有
L1??G2H1，L2??G1G2H2，L3??G1G2，L4??G3，L5?G3H1G2H2， ??1?(L1?L2?L3?L4?L5)，C(s)P1?1?P2?2 ?R(s)??G1G2?G3
1?G2H1?G1G2H2?G1G2?G3?G3H1G2H2（e）图中有2条前向通路，3个回路，有1对互不接触回路
P，P2??G4G3，?2?1?L1，1?G1G2G3，?1?1 L1??G1G2H1，L2??G3H2，L3??G2H3， ??1?(L1?L2?L3)?L1L2，则有
G1G2G3?G4G3(1?G1G2H1)C(s)P1?1?P2?2 ??R(s)?1?G1G2H1?G3H2?G2H3?G1G2G3H1H2
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