1-24 The problem of a circle is different from that of a stroke, because it connects points instead of lines.

The solution to this problem is as follows, absolutely original:

Paint some points black so that black and white are not adjacent, as shown in the figure.

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Assuming that there is a line that can meet the requirements, the following two points are correct:

1 After straightening this line, there are 24 dots * * * on it, and it is black and white. Because it is black and white, the number of black spots can only be more than that of white spots 1.

2 As can be seen from the figure, there are 13 black spots and 1 1 white spots among the 24 points, and there are 2 more black spots than white spots;

1 and 2 are contradictory, so the assumption is wrong, that is, no line can meet the requirements of the topic;

2-The problem of the Seven Bridges is a passing problem, and there is no solution that can be summed up as whether the following picture can be drawn in one stroke:

As everyone said, there are four singularities in ABCD, more than two, so it takes at least 4/2=2 strokes to complete.

Thank you!