FastPrep
Problem · Array

Chunked Byte Stream Checksums

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Problem statement

An integer array stream encodes consecutive chunks. Each chunk starts with one header byte k, followed by exactly k data bytes.

For every chunk, compute the unsigned byte-sum checksum:

checksum = (sum of the chunk's data bytes) modulo 256

The header byte is not part of the checksum. Return the checksums in chunk order. A zero-length chunk has checksum 0.

Function

computeChecksums(stream: int[]) → int[]

Examples

Example 1

stream = [3,10,20,30,2,255,2]return = [60,1]

The first chunk sums to 60. The second sums to 257, whose remainder modulo 256 is 1.

Example 2

stream = [0,1,7,4,100,100,100,100]return = [0,7,144]

The chunks contain zero, one, and four data bytes. The last checksum is 400 modulo 256 = 144.

Constraints

  • 1 <= stream.length <= 10^5.
  • Every value is an integer from 0 through 255.
  • The stream is valid: each header is followed by exactly its declared number of data bytes, and the final chunk ends at the end of the array.

More Upstart problems

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public int[] computeChecksums(int[] stream) {
    // Write your code here.
}
stream[3,10,20,30,2,255,2]
expected[60,1]
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