Language Syntax

The minimal vocabulary — declarations, literals, operators, indexing — that you must type without thinking so the editor never becomes the bottleneck during a timed problem.

Why it matters

Syntax recall is the difference between transcribing an algorithm you already see and stalling on “how do I slice this again?” The handful of constructs below cover ~95% of what any DSA solution needs; the rest you can look up. Getting integer semantics and slicing exactly right also kills a whole class of silent wrong-answer bugs that no compiler will catch for you.

How it works

The DSA-relevant syntax reduces to a small core. Pin down the exact behavior in your chosen language:

Concept	Python	C++	Watch for
Integer division	7 // 2 == 3	7 / 2 == 3	C++ truncates toward 0; Python floors
Negative mod	-7 % 3 == 2	-7 % 3 == -1	sign differs across languages
Subarray slice	a[2:5]	a.substr(2,3)	half-open vs offset+length
Swap	a, b = b, a	swap(a, b)	tuple-unpack vs library call
Int max	float('inf')	INT_MAX	C++ INT_MAX + 1 overflows (UB)

• Slicing is half-open [lo, hi) in most languages: a[2:5] yields 3 elements (indices 2, 3, 4). This convention is why hi - lo is the length and why off-by-one bugs cluster at boundaries.
• Negative indexing (a[-1] for the last element) exists in Python/Ruby but not C/C++/Java — porting code across languages breaks here.
• Use language-native multiple assignment for swaps and two-pointer updates; it is both shorter and avoids a temp-variable bug.

Example

Reverse an array in place using only core syntax:

lo, hi = 0, len(a) - 1
while lo < hi:
    a[lo], a[hi] = a[hi], a[lo]   # simultaneous swap, no temp
    lo, hi = lo + 1, hi - 1

The same loop in C++ needs std::swap(a[lo], a[hi]) and explicit ++lo; --hi;.

Pitfalls

• Integer division and modulo on negatives differ by language. -7 % 3 is 2 in Python but -1 in C++/Java/Go — this breaks hashing and circular-buffer index math.
• Fixed-width integer overflow is silent. INT_MAX + 1 in C++/Java wraps (or is UB); a sum of large values needs long/int64. Python integers are unbounded, so this bug only appears after porting.
• Slice endpoints are exclusive. Reading a[lo:hi] as inclusive double-counts or skips the boundary element.
• Chained comparisons like 0 <= i < n mean what you expect in Python but are a bug in C/C++ (parsed as (0 <= i) < n).

See also

• control-structures
• functions
• basic-data-structures