Back to All Blogs1 min read11 Sept 2026
DSA Patterns That Actually Matter · Part 3 of 5
Binary Search on the Answer: Search the Solution Space
“Use monotonic feasibility checks for optimization problems.”
Binary Search on the Answer
Binary search can work on any ordered solution space where a condition changes monotonically.
false false false false true true true
↑
first valid answerTemplate
let low = minimumPossible;
let high = maximumPossible;
while (low < high) {
const mid = Math.floor((low + high) / 2);
if (canDo(mid)) {
high = mid;
} else {
low = mid + 1;
}
}
return low;The Real Work
Define the search space, the feasibility check and monotonicity.
Warning
If the predicate is not monotonic, binary search cannot safely discard half of the search space.
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