Binary Search on the Answer
When you can quickly test whether a candidate answer works, and bigger candidates never hurt, binary search the answer itself.
The problem
A shop must ship n packages in order, one after another, within days days. The ship carries at most cap weight per day, and a package cannot be split. What is the smallest capacity that finishes on time?
For weights 3 2 2 4 1 4 and 3 days the answer is 6.
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