Interview 150
Peak Index in a Mountain Array
- Problem
- LC 852
- File
- interview150_LC852PeakIndexInMountainArray.java
- Path
- pkg5leetcode/interview150/interview150_LC852PeakIndexInMountainArray.java
- Package
- pkg5leetcode.interview150
- Command
- java pkg5leetcode/interview150/interview150_LC852PeakIndexInMountainArray.java
- Approach
- Binary search where mid slope points uphill.
- Complexity
- Time O(log n), Space O(1)
There is no in-browser runner. This is the file from the curriculum, unchanged.
1package pkg5leetcode.interview150;2 3/*4 * Peak Index in a Mountain Array | LC 8525 * APPROACH: Binary search where mid slope points uphill.6 * COMPLEXITY: Time O(log n), Space O(1)7 */8public class interview150_LC852PeakIndexInMountainArray {9 static int peakIndexInMountainArray(int[] arr) {10 int lo = 0, hi = arr.length - 1;11 while (lo < hi) {12 int mid = lo + (hi - lo) / 2;13 if (arr[mid] < arr[mid + 1]) lo = mid + 1;14 else hi = mid;15 }16 return lo;17 }18 19 public static void main(String[] args) {20 check(peakIndexInMountainArray(new int[]{0, 1, 0}) == 1, "case1");21 check(peakIndexInMountainArray(new int[]{0, 2, 1, 0}) == 1, "case2");22 System.out.println("all tests passed");23 }24 25 static void check(boolean cond, String name) {26 if (!cond) throw new AssertionError("FAILED: " + name);27 System.out.println(" PASS " + name);28 }29}