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CCC Python Course

Difference arrays and interval clamping

Stage
4
Module
M4.4
Lessons
1

In this module

  • Use a difference array to apply multiple range updates efficiently.
  • Solve problems where you increment or decrement a range of elements.
  • Recognize the dual relationship between prefix sums and difference arrays.
  • Handle boundary conditions in difference arrays correctly.

Before this module

M4.3Prefix sums (1D, 2D, prefix/suffix max)

Lessons

  1. 1Difference arrays and interval clamping

Practice

Try this on the judge. The link opens the problem on WMOJ.

  1. 2026 J5
    Beams of Light (opens on WMOJ in a new tab) WMOJ(same problem as 2026 S2)

    Apply a +1/-1 update at each interval's clipped ends and answer queries in O(1) with a prefix sum.