Shannon coding. I have attached the test case below. My code keeps failing with the wrong encoding. Can someone help please with the full code?

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TEST $1$

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Your output is incorrect.

Your program tested with:

Input string:

COSC $3360$ COSC $1437$

COSC $1336$ COSC $2436$

COSC $3320$ COSC $3380$

YOUR OUTPUT:

Message: COSC $3360$ COSC $1437$

Alphabet:

Symbol: C$,$ Frequency: $4,$ Shannon code: $000$

Symbol: $3,$ Frequency: $3,$ Shannon code: $001$

Symbol: $,$ Frequency: $3,$ Shannon code: $01$

Symbol: S$,$ Frequency: $2,$ Shannon code: $100$

Symbol: O$,$ Frequency: $2,$ Shannon code: $101$

Symbol: $7,$ Frequency: $1,$ Shannon code: $1100$

Symbol: $6,$ Frequency: $1,$ Shannon code: $1101$

Symbol: $4,$ Frequency: $1,$ Shannon code: $1110$

Symbol: $1,$ Frequency: $1,$ Shannon code: $11110$

Symbol: $0,$ Frequency: $1,$ Shannon code: $11111$

Encoded message: $0001011000000100100111011111101000101100000011111011100011100$

Message: COSC $1336$ COSC $2436$

Alphabet:

Symbol: C$,$ Frequency: $4,$ Shannon code: $000$

Symbol: $3,$ Frequency: $3,$ Shannon code: $001$

Symbol: $,$ Frequency: $3,$ Shannon code: $01$

Symbol: S$,$ Frequency: $2,$ Shannon code: $100$

Symbol: O$,$ Frequency: $2,$ Shannon code: $101$

Symbol: $6,$ Frequency: $2,$ Shannon code: $110$

Symbol: $4,$ Frequency: $1,$ Shannon code: $1110$

Symbol: $2,$ Frequency: $1,$ Shannon code: $11110$

Symbol: $1,$ Frequency: $1,$ Shannon code: $11111$

Encoded message: $00010110000001111110010011100100010110000001111101110001110$

Message: COSC $3320$ COSC $3380$

Alphabet:

Symbol: C$,$ Frequency: $4,$ Shannon code: $000$

Symbol: $3,$ Frequency: $4,$ Shannon code: $001$

Symbol: $,$ Frequency: $3,$ Shannon code: $01$

Symbol: S$,$ Frequency: $2,$ Shannon code: $100$

Symbol: O$,$ Frequency: $2,$ Shannon code: $101$

Symbol: $0,$ Frequency: $2,$ Shannon code: $110$

Symbol: $8,$ Frequency: $1,$ Shannon code: $1110$

Symbol: $2,$ Frequency: $1,$ Shannon code: $1111$

Encoded message: $00010110000001001001111111001000101100000010010011110110$

CORRECT OUTPUT:

Message: COSC $3360$ COSC $1437$

Alphabet:

Symbol: C$,$ Frequency: $4,$ Shannon code: $000$

Symbol: $3,$ Frequency: $3,$ Shannon code: $001$

Symbol: $,$ Frequency: $3,$ Shannon code: $010$

Symbol: S$,$ Frequency: $2,$ Shannon code: $1000$

Symbol: O$,$ Frequency: $2,$ Shannon code: $1010$

Symbol: $7,$ Frequency: $1,$ Shannon code: $10111$

Symbol: $6,$ Frequency: $1,$ Shannon code: $11001$

Symbol: $4,$ Frequency: $1,$ Shannon code: $11010$

Symbol: $1,$ Frequency: $1,$ Shannon code: $11100$

Symbol: $0,$ Frequency: $1,$ Shannon code: $11110$

Encoded message: $00010101000000010001001110011111001000010101000000010111001101000110111$

Message: COSC $1336$ COSC $2436$

Alphabet:

Symbol: C$,$ Frequency: $4,$ Shannon code: $000$

Symbol: $3,$ Frequency: $3,$ Shannon code: $001$

Symbol: $,$ Frequency: $3,$ Shannon code: $010$

Symbol: S$,$ Frequency: $2,$ Shannon code: $1000$

Symbol: O$,$ Frequency: $2,$ Shannon code: $1010$

Symbol: $6,$ Frequency: $2,$ Shannon code: $1011$

Symbol: $4,$ Frequency: $1,$ Shannon code: $11010$

Symbol: $2,$ Frequency: $1,$ Shannon code: $11100$

Symbol: $1,$ Frequency: $1,$ Shannon code: $11110$

Encoded message: $000101010000000101111000100110110100001010100000001011100110100011011$

Message: COSC $3320$ COSC $3380$

Alphabet:

Symbol: C$,$ Frequency: $4,$ Shannon code: $000$

Symbol: $3,$ Frequency: $4,$ Shannon code: $001$

Symbol: $,$ Frequency: $3,$ Shannon code: $011$

Symbol: S$,$ Frequency: $2,$ Shannon code: $1001$

Symbol: O$,$ Frequency: $2,$ Shannon code: $1010$

Symbol: $0,$ Frequency: $2,$ Shannon code: $1100$

Symbol: $8,$ Frequency: $1,$ Shannon code: $11100$

Symbol: $2,$ Frequency: $1,$ Shannon code: $11110$

Encoded message: $0001010100100001100100111110110001100010101001000011001001111001100$