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Challenges The 50 substrings that validate any string of Roman numerals

Bash, 118 bytes same regex as my Perl answer the longer version here is pure bash, the short one calls out to POSIX(ish) utilities grep -Eo '([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I...

posted 6mo ago by jhnc‭  ·  edited 6mo ago by jhnc‭

Answer
#5: Post edited by user avatar jhnc‭ · 2026-03-11T18:18:32Z (6 months ago)
  • # [Bash], 118 bytes
  • * same regex as my Perl answer
  • * the longer version here is pure bash, the short one calls out to POSIX(ish) utilities
  • <!-- language-all: lang-bash -->
  • grep -Eo '([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]'|sed q
  • * -E - use POSIX ERE regex flavour
  • * -o (non-standard) - outputs each match on separate line
  • [Try it online!][TIO-mmmczek1]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmmczek1]: https://tio.run/##bVPBitswEL3rK4Y0ZRNIDktvLe1SRj0IRlcx4PqwbZwmsCRbJ9DDer99@2bs9YpSQ@Qn672nNxrlx/3l8PKO9ueert3lSof7/tRdLmG/Wj8FwtN/Xq66n4czLZa3CxpefvXdI22/nelm1XDK2q6/3z59eB644dw2MbdAGHlITdK2KdoCYUxDSXc@VVDF3qJDE7XlO5c1SUrbcJQRa6ugtTfDpdvR7/9FtHRrH5uGtida9tS2NAz02B9P1z2Vr5Kir0/5@0V4Dn8Ox4eO@u5@Rw/HU/eJdmfnTKLF@wttv9ACdFte@NqefBJ251P3kujjZF1mpDOSGfGM4ozyjFJl4z4laOViNiKBKxNzibCoPSqTCqdiGCMY5o0RTm/rzKXCWuEqfbU1s@2NESg7yra3b4InZImGBeFUTYYxRE5JnaEhs6pXZy/M8KhnNISKRHnMD4Bp5qyc3nLhSwRRIC51zdmcVN6KcWGpCRpHgTo7wvYffY4wHWvaEGZBqzawiI6NACvmbMQInvqZxJjy1JUNJZPjhIqwpqKZi4qfoG6oyIaEIcshFkm45yhfS5ZUERJ@BSaFcSHwJ0D7UHD0MAWf40hRvAU06260485ml0XmcMYSM@ORCQ4GtAyHg@0tuOCvx1PwORwwPm@sB16KIQk4QGVzhzJ79z1NJbK9PJHrsm8muB/YN0Jl@eZTetW@VjPnA3tjV8XEdtez69GfyH7hTRzz5I9PtSx66@JY5RTdbt1f "Bash – Try It Online"
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
  • # [Bash], 118 bytes
  • * same regex as my Perl answer
  • * the longer version here is pure bash, the short one calls out to POSIX(ish) utilities
  • <!-- language-all: lang-bash -->
  • grep -Eo '([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]'|sed q
  • * `-E` - use POSIX ERE regex flavour
  • * `-o` (non-standard) - outputs each match on separate line
  • [Try it online!][TIO-mmmczek1]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmmczek1]: https://tio.run/##bVPBitswEL3rK4Y0ZRNIDktvLe1SRj0IRlcx4PqwbZwmsCRbJ9DDer99@2bs9YpSQ@Qn672nNxrlx/3l8PKO9ueert3lSof7/tRdLmG/Wj8FwtN/Xq66n4czLZa3CxpefvXdI22/nelm1XDK2q6/3z59eB644dw2MbdAGHlITdK2KdoCYUxDSXc@VVDF3qJDE7XlO5c1SUrbcJQRa6ugtTfDpdvR7/9FtHRrH5uGtida9tS2NAz02B9P1z2Vr5Kir0/5@0V4Dn8Ox4eO@u5@Rw/HU/eJdmfnTKLF@wttv9ACdFte@NqefBJ251P3kujjZF1mpDOSGfGM4ozyjFJl4z4laOViNiKBKxNzibCoPSqTCqdiGCMY5o0RTm/rzKXCWuEqfbU1s@2NESg7yra3b4InZImGBeFUTYYxRE5JnaEhs6pXZy/M8KhnNISKRHnMD4Bp5qyc3nLhSwRRIC51zdmcVN6KcWGpCRpHgTo7wvYffY4wHWvaEGZBqzawiI6NACvmbMQInvqZxJjy1JUNJZPjhIqwpqKZi4qfoG6oyIaEIcshFkm45yhfS5ZUERJ@BSaFcSHwJ0D7UHD0MAWf40hRvAU06260485ml0XmcMYSM@ORCQ4GtAyHg@0tuOCvx1PwORwwPm@sB16KIQk4QGVzhzJ79z1NJbK9PJHrsm8muB/YN0Jl@eZTetW@VjPnA3tjV8XEdtez69GfyH7hTRzz5I9PtSx66@JY5RTdbt1f "Bash – Try It Online"
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
#4: Post edited by user avatar jhnc‭ · 2026-03-11T18:18:02Z (6 months ago)
sed is shorter than head
  • # [Bash], 120 bytes
  • * same regex as my Perl answer
  • * the longer version here is pure bash, the short one calls out to POSIX(ish) utilities
  • <!-- language-all: lang-bash -->
  • grep -Eo '([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]'|head -1
  • * `-E` - use POSIX ERE regex flavour
  • * `-o` (non-standard) - outputs each match on separate line
  • [Try it online!][TIO-mmjg1ipq]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjg1ipq]: https://tio.run/##bVPBahsxEL3rK4TrEgfsQ@itpQ1lpgfB6CoGtntw6nUdCHZYG3rI5tvTN7ObtShdsPZp9d7TG438sD0f3j7E/amPl@58iYdtf@zO57Bf3b6EiKf/ulx1vw6nuFjeLeLw9rvvnuPmxynerBpKWdvbn3cvn14Haii3DecWCCMNqUnaNkVbIIxpKOnepwqq2Ft0aFhbundZk6S0DbGMWFsFrb0ZDt12Fzd3/wtp@W59bJq4OcZlH9s2DkN87h@Pl30s3yWxr08V9IvwGv4cHp@62Jvt0@Ox@xJ3J@dMosXHc9x8iwvQbXnha/vok7A7Hbu3FD9P1mVGOiOZEc2IZ5RnlCob9ylBKxezEQlUmZgLw6L2qEwqnIphjGCYN0Y4XdeJSoW1wlX6amsi2xsjUHaUbW/fBE/IwoYF4VRNhjEwpaTO0JBJ1auzF2Z41DMaQkWiNOYHwDRTVkrXXPjCIArEpa45m5PKtRgXlpqgPArU2Qzbf/SZYTrWtI6YBa3aQCI6NgIsztmIDJ76mTCnPHVlHZPJcUJFSFPRTEXFT1DXscg6CkGWAxdJuOkoX0uWVBESfgUmhXAh8DdA@1Awe5iCzzxSFG8BzbrLdtzZ7LLIHM5YYmY0MsHBgJbhcLC9BRf8@WgKPocDxue19cBLMSQBB6hk7lBm776nqUS2lydyXfbNBPcD@zJUlm8@pXftezVzPrDXdlVMbHc9ux79YfILb2LOkz8@1TL21vFY5RTdbt1f "Bash – Try It Online"
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
  • # [Bash], 118 bytes
  • * same regex as my Perl answer
  • * the longer version here is pure bash, the short one calls out to POSIX(ish) utilities
  • <!-- language-all: lang-bash -->
  • grep -Eo '([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]'|sed q
  • * -E - use POSIX ERE regex flavour
  • * -o (non-standard) - outputs each match on separate line
  • [Try it online!][TIO-mmmczek1]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmmczek1]: https://tio.run/##bVPBitswEL3rK4Y0ZRNIDktvLe1SRj0IRlcx4PqwbZwmsCRbJ9DDer99@2bs9YpSQ@Qn672nNxrlx/3l8PKO9ueert3lSof7/tRdLmG/Wj8FwtN/Xq66n4czLZa3CxpefvXdI22/nelm1XDK2q6/3z59eB644dw2MbdAGHlITdK2KdoCYUxDSXc@VVDF3qJDE7XlO5c1SUrbcJQRa6ugtTfDpdvR7/9FtHRrH5uGtida9tS2NAz02B9P1z2Vr5Kir0/5@0V4Dn8Ox4eO@u5@Rw/HU/eJdmfnTKLF@wttv9ACdFte@NqefBJ251P3kujjZF1mpDOSGfGM4ozyjFJl4z4laOViNiKBKxNzibCoPSqTCqdiGCMY5o0RTm/rzKXCWuEqfbU1s@2NESg7yra3b4InZImGBeFUTYYxRE5JnaEhs6pXZy/M8KhnNISKRHnMD4Bp5qyc3nLhSwRRIC51zdmcVN6KcWGpCRpHgTo7wvYffY4wHWvaEGZBqzawiI6NACvmbMQInvqZxJjy1JUNJZPjhIqwpqKZi4qfoG6oyIaEIcshFkm45yhfS5ZUERJ@BSaFcSHwJ0D7UHD0MAWf40hRvAU06260485ml0XmcMYSM@ORCQ4GtAyHg@0tuOCvx1PwORwwPm@sB16KIQk4QGVzhzJ79z1NJbK9PJHrsm8muB/YN0Jl@eZTetW@VjPnA3tjV8XEdtez69GfyH7hTRzz5I9PtSx66@JY5RTdbt1f "Bash – Try It Online"
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
#3: Post edited by user avatar jhnc‭ · 2026-03-09T17:22:10Z (6 months ago)
use external utilities
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • * same regex as my Perl answer
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
  • # [Bash], 120 bytes
  • * same regex as my Perl answer
  • * the longer version here is pure bash, the short one calls out to POSIX(ish) utilities
  • <!-- language-all: lang-bash -->
  • grep -Eo '([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL]'|head -1
  • * `-E` - use POSIX ERE regex flavour
  • * `-o` (non-standard) - outputs each match on separate line
  • [Try it online!][TIO-mmjg1ipq]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjg1ipq]: https://tio.run/##bVPBahsxEL3rK4TrEgfsQ@itpQ1lpgfB6CoGtntw6nUdCHZYG3rI5tvTN7ObtShdsPZp9d7TG438sD0f3j7E/amPl@58iYdtf@zO57Bf3b6EiKf/ulx1vw6nuFjeLeLw9rvvnuPmxynerBpKWdvbn3cvn14Haii3DecWCCMNqUnaNkVbIIxpKOnepwqq2Ft0aFhbundZk6S0DbGMWFsFrb0ZDt12Fzd3/wtp@W59bJq4OcZlH9s2DkN87h@Pl30s3yWxr08V9IvwGv4cHp@62Jvt0@Ox@xJ3J@dMosXHc9x8iwvQbXnha/vok7A7Hbu3FD9P1mVGOiOZEc2IZ5RnlCob9ylBKxezEQlUmZgLw6L2qEwqnIphjGCYN0Y4XdeJSoW1wlX6amsi2xsjUHaUbW/fBE/IwoYF4VRNhjEwpaTO0JBJ1auzF2Z41DMaQkWiNOYHwDRTVkrXXPjCIArEpa45m5PKtRgXlpqgPArU2Qzbf/SZYTrWtI6YBa3aQCI6NgIsztmIDJ76mTCnPHVlHZPJcUJFSFPRTEXFT1DXscg6CkGWAxdJuOkoX0uWVBESfgUmhXAh8DdA@1Awe5iCzzxSFG8BzbrLdtzZ7LLIHM5YYmY0MsHBgJbhcLC9BRf8@WgKPocDxue19cBLMSQBB6hk7lBm776nqUS2lydyXfbNBPcD@zJUlm8@pXftezVzPrDXdlVMbHc9ux79YfILb2LOkz8@1TL21vFY5RTdbt1f "Bash – Try It Online"
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
#2: Post edited by user avatar jhnc‭ · 2026-03-09T17:03:49Z (6 months ago)
optimise regex
  • # [Bash], 139 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ CCCC|C[CM][DM]|C[DM]C|IIII|I[IX][VX]|I[VX]I|MMMM|VI?[VX]|XC[CLX]|XLX|XXXX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • * same regex as my Perl answer
  • [Try it online!][TIO-mmidz6p3]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmidz6p3]: https://tio.run/##bVPRahsxEHzXVyxOGlpwHvra0oZ0txDB6qUtYuE4ipOccSDYxQ70odf@ejq751yUUoHlOd3MaFaru14dNo8ntN7t6WE4PNBmtd8Oh0Nav37zKxFG19GKPvyha@p7OqGb@2G1p0@XX6@@f/lcLr/x1SMYp2@dwhgjd1z6TkoPhJnHjDHmLlvfVeuBMOexYIw1X8SaQaT@rzYaxtiJ9XwRLl3W2ncsOmHrDdweYc7OhpvNjk5fZPlPJccizrcvqV7OOFJ41EvNkn6nn5u7@4H2w@qW7u@2w3u63YX8x/5u@7CmxasDnX@kBS1O/fUi3q0pHtLtbjs8Znp3NKszshnpjHhGMqMyo9zYhE9N1ri4jWrixsRdBBatR2PS4FwdYwbDvTHD6fk9c22wNbhJ32zN7HtjBiqBiu8dm2CkouJYEc7MZZiTcM4WDEuFvePxwvwJwyKjI1SkxlN@ADwWLsb5ORdWBESFuLY1F3cyfS4mhLUlmEwCC7bA9h99EZhONS0JT8maNrCqTY0AS0pxooBncSYiuRy7sqTscpxQVbZcrXA1jRO0JVVdkjJkJUnVjMuO8q0WzQ0h41dhUhkXAl8C2oeCJcJULMtEMfwraN5d8eMubldU53DOUjfjiQkOJrQMh4PtPbjiI@Rj8DkcMJaX3oMoxZEmHKCxu0NZovuRphH5XpEodCU2U9wP7CtQeb75lJ60T9XM@cBe@lVxsd/1Enr0RzguvIulHP2x1MokWidTlcfofuv@Ag "Bash – Try It Online"
  • # [Bash], 133 bytes
  • <!-- language-all: lang-bash -->
  • [[ $1 =~ ([CIMX])\1{3}|C[CM][DM]|C[DM]C|I[IX][VX]|I[VX]I|VI?[VX]|XC[CLX]|XLX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH
  • * same regex as my Perl answer
  • [Try it online!][TIO-mmjfjg3l]
  • [Bash]: https://www.gnu.org/software/bash/
  • [TIO-mmjfjg3l]: https://tio.run/##bVPRahsxEHzXVyxOGhK4PIS@taTBXRUiWL20RSxcj@IkZxwIdrENfYjTX3dn95yzUnpg3Ug3M5rVynezzWJ/QvPVmrb9ZkuL2XrZbzZhfn7xHAhP29KMrv/QHXUdndD9Uz9b0@fpt9ufX7/k6Xe@3YNxemWU85ZT1u7ix9Xz@5cdt5y7NuYOCCPvUpu0a4t2QBjTrqQbnyqoYm/RXRu14xuXtUlK13KUAWunoHWIcXbW3y9WdPomxX9qOMS/XL6lWiG7HblHmUqK4SX8Xjw@9bTuZw/09LjsP9LDyuW/1o/L7Zwm7zZ0@YkmNDm1zxP/NiefhIfVst8n@nAwKyPSEcmIeERxRHlEqbJxnxK0cjEbkcCViblEWNQelUmFUzGMEQzzxgin43fmUmGtcJW@2prZ9sYIlB1l29s3wROyRMOCcKomwxgip6TO0JBZ1auzF2Z41DMaQkWiPOQHwDRzVk7HXFiJIArEpa45m5PKsRgXlpqgcRCosyNs/9HnCNOhpoYwC1q1gUV0aARYMWcjRvDUzyTGlA9daSiZHCdUhDUVzVxU/AS1oSINCUOWQyyScNlRvpYsqSIk/ApMCuNC4J@A9qHg6GEKluNAUbwFNOtutOPOZpdFxnDGEjPjgQkOBrQMh4PtLbjg/8eH4GM4YCw31gMvxZAEHKCyuUOZvfuephLZXp7Iddk3E9wP7BuhsnzjKb1qX6sZ84Hd2FUxsd317Hr0J7JfeBPHfPDHUi2L3ro4VHmIbrfuLw "Bash – Try It Online"
#1: Initial revision by user avatar jhnc‭ · 2026-03-08T23:33:05Z (6 months ago) 
# [Bash], 139 bytes

<!-- language-all: lang-bash -->

    [[ $1 =~ CCCC|C[CM][DM]|C[DM]C|IIII|I[IX][VX]|I[VX]I|MMMM|VI?[VX]|XC[CLX]|XLX|XXXX|[DX]C?[DM]|[ILV][CDLM]|[ILX]X[CL] ]]&&echo $BASH_REMATCH

* same regex as my Perl answer

[Try it online!][TIO-mmidz6p3]

[Bash]: https://www.gnu.org/software/bash/
[TIO-mmidz6p3]: https://tio.run/##bVPRahsxEHzXVyxOGlpwHvra0oZ0txDB6qUtYuE4ipOccSDYxQ70odf@ejq751yUUoHlOd3MaFaru14dNo8ntN7t6WE4PNBmtd8Oh0Nav37zKxFG19GKPvyha@p7OqGb@2G1p0@XX6@@f/lcLr/x1SMYp2@dwhgjd1z6TkoPhJnHjDHmLlvfVeuBMOexYIw1X8SaQaT@rzYaxtiJ9XwRLl3W2ncsOmHrDdweYc7OhpvNjk5fZPlPJccizrcvqV7OOFJ41EvNkn6nn5u7@4H2w@qW7u@2w3u63YX8x/5u@7CmxasDnX@kBS1O/fUi3q0pHtLtbjs8Znp3NKszshnpjHhGMqMyo9zYhE9N1ri4jWrixsRdBBatR2PS4FwdYwbDvTHD6fk9c22wNbhJ32zN7HtjBiqBiu8dm2CkouJYEc7MZZiTcM4WDEuFvePxwvwJwyKjI1SkxlN@ADwWLsb5ORdWBESFuLY1F3cyfS4mhLUlmEwCC7bA9h99EZhONS0JT8maNrCqTY0AS0pxooBncSYiuRy7sqTscpxQVbZcrXA1jRO0JVVdkjJkJUnVjMuO8q0WzQ0h41dhUhkXAl8C2oeCJcJULMtEMfwraN5d8eMubldU53DOUjfjiQkOJrQMh4PtPbjiI@Rj8DkcMJaX3oMoxZEmHKCxu0NZovuRphH5XpEodCU2U9wP7CtQeb75lJ60T9XM@cBe@lVxsd/1Enr0RzguvIulHP2x1MokWidTlcfofuv@Ag "Bash – Try It Online"