f1（1^n01^m）=1^ m-n|
设计计算功能的图灵机（转换图）
如何跟踪中间的0？
我试过了，但想不出来
最佳答案
我假设您希望磁带字母表只包含0、1和-（空白）。在使用单磁带图灵机时，我们的策略是卓有成效的：我们将在中间的0附近来回反弹，在找到1时将其划掉。我们将继续，直到1s用完并达到空白。在这一点上，磁带上剩下的是1^ m-n以及n+m+1-m-n零。最后，我们将结果复制到磁带的开头（如果它不在原来的位置，即m>n），并删除零。
Q s s' D Q'
// read past 1^n
q0 1 1 R q0
// read through zeroes
q0 0 0 R q1
q1 0 0 R q1
// mark out the first 1 remaining in 1^m
q1 1 0 L q2
// read through zeros backwards
q2 0 0 L q2
// mark out the last 1 remaining in 1^n
q2 1 0 R q1
// we were reading through zeroes forward
// and didn't find another 1. n >= m and
// we have deleted the same number from
// the first and last parts so just delete
// zeroes
q1 - - L q3
q3 0 - L q3
q3 1 1 L halt_accept
// we were reading through zeroes backwards
// and didn't find another 1. n < m and we
// accidentally deleted one too many symbols
// from the 1^m part. write it back and start
// copying the 1s from after the 0s back to
// the beginning of the tape. then, clear zeroes.
q2 - - R q4
q4 0 1 R q5
q5 0 0 R q5
q5 1 0 L q6
q6 0 0 L q6
q6 1 1 R q4
q5 - - L q7
q7 0 - L q7
q7 1 1 L halt_accept
当然，如果没有一个执行的例子，就没有一个TM示例是完整的。
-111110111- => -111110111- => -111110111-
^ ^ ^
q0 q0 q0
=> -111110111- => -111110111- => -111110111-
^ ^ ^
q0 q0 q0
=> -111110111- => -111110011- => -111110011-
^ ^ ^
q1 q2 q2
=> -111100011- => -111100011- => -111100011-
^ ^ ^
q1 q1 q1
=> -111100001- => -111100001- => -111100001-
^ ^ ^
q2 q2 q2
=> -111100001- => -111000001- => -111000001-
^ ^ ^
q1 q1 q1
=> -111000001- => -111000001- => -111000001-
^ ^ ^
q1 q1 q1
=> -111000000- => -111000000- => -111000000-
^ ^ ^
q2 q2 q2
=> -111000000- => -111000000- => -111000000-
^ ^ ^
q2 q2 q2
=> -110000000- => -110000000- => -110000000-
^ ^ ^
q1 q1 q1
=> -110000000- => -110000000- => -110000000-
^ ^ ^
q1 q1 q1
=> -110000000- => -110000000- => -11000000--
^ ^ ^
q1 q3 q3
=> -1100000--- => -110000---- => -11000-----
^ ^ ^
q1 q3 q3
=> -1100------ => -110------- => -11--------
^ ^ ^
q1 q3 q3
=> -11--------
^
halt_accept