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702. Search in a Sorted Array of Unknown Size 👍

  • Time: $O(\log 10^4)$
  • Space: $O(1)$
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/**
 * // This is the ArrayReader's API interface.
 * // You should not implement it, or speculate about its implementation
 * class ArrayReader {
 *  public:
 *   int get(int index);
 * };
 */

class Solution {
 public:
  int search(const ArrayReader& reader, int target) {
    int l = 0;
    int r = 10'000;

    while (l < r) {
      const int m = (l + r) / 2;
      if (reader.get(m) >= target)
        r = m;
      else
        l = m + 1;
    }

    return reader.get(l) == target ? l : -1;
  }
};

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/**
 * // This is ArrayReader's API interface.
 * // You should not implement it, or speculate about its implementation
 * interface ArrayReader {
 *   public int get(int index) {}
 * }
 */

class Solution {
  public int search(ArrayReader reader, int target) {
    int l = 0;
    int r = 10000;

    while (l < r) {
      final int m = (l + r) / 2;
      if (reader.get(m) >= target)
        r = m;
      else
        l = m + 1;
    }

    return reader.get(l) == target ? l : -1;
  }
}

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# """
# This is ArrayReader's API interface.
# You should not implement it, or speculate about its implementation
# """
# Class ArrayReader:
#   def get(self, index: int) -> int:

class Solution:
  def search(self, reader: 'ArrayReader', target: int) -> int:
    l = bisect.bisect_left(range(10**4), target,
                           key=lambda m: reader.get(m))
    return l if reader.get(l) == target else -1