I need to make a stack trace like the one shown below to determine if the braces are balanced. I am unsure about how it works exactly. The pseudocode is below the picture.

1. Please explain why and how the braces are changing in each step? -- Why did the brace between b and c disappear in the second step and shift to a backwards brace in the third step (why is a and b together in the third step?)

2. why do the boxes start out as four and decrese by one each time?

3. Why is the last example not balanced?

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