Binary Search First Occurrence

Find the first copy of a duplicated target by recording matches and continuing to search the left half.

Algorithm

Basic Implementation

basic.R

arr <- c(1, 2, 4, 4, 4, 7, 9)
target <- 4
lo <- 0
hi <- length(arr) - 1
result <- -1
while (lo <= hi) {
  mid <- lo + (hi - lo) %/% 2
  value <- arr[mid + 1]
  if (value == target) {
    result <- mid
    hi <- mid - 1
  } else if (value < target) {
    lo <- mid + 1
  } else {
    hi <- mid - 1
  }
}
cat(result, "\n", sep = "")

Complexity

Time: O(log n)
Space: O(1)

Implementation notes

Keep the explicit control flow. Library shortcuts would hide the state changes this lesson is meant to replay.
The final output is intentionally small and deterministic for cross-language comparison.

execution replay The checked-in replay follows the language-neutral state table for `search-binary-first`.

cross-language comparison This R DSA version keeps the same data and final output as every other DSA book in this wave.