add example of malloc

[richa7327]

• I have read freeCodeCamp's contribution guidelines.
• My pull request has a descriptive title (not a vague title like Update index.md)
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If your pull request closes a GitHub issue, replace the XXXXX below with the issue number.

Closes #XXXXX

[RandellDawson]

Closed and Reopened this PR to attempt to resolve a specific Travis build failure.

[cmccormack]

This looks good to me 👍. Thank you for your contribution!