DSA/findInMountainArray.java at main · Anurag-1401/DSA · GitHub

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

class Solution {
    public int findInMountainArray(int target, MountainArray arr) {
        int n = arr.length();

        int l = 0, r = n - 1;
        while (l < r) {
            int mid = l + (r - l) / 2;

            if (arr.get(mid) < arr.get(mid + 1)) {
                l = mid + 1;
            } else {
                r = mid;
            }
        }

        int peak = l;

        int res = binarySearch(arr, target, 0, peak, true);
        if (res != -1) return res;

        return binarySearch(arr, target, peak + 1, n - 1, false);
    }

    private int binarySearch(MountainArray arr, int target, int l, int r, boolean asc) {
        while (l <= r) {
            int mid = l + (r - l) / 2;
            int val = arr.get(mid);

            if (val == target) return mid;

            if (asc) {
                if (val < target) l = mid + 1;
                else r = mid - 1;
            } else {
                if (val < target) r = mid - 1;
                else l = mid + 1;
            }
        }
        return -1;
    }
}