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Ice Cream Parlor

  • Kanahaiya
     + 3 comments

    Hello friends,

    In this video, I have solved hackerrank Ice Cream Parlor problem in an easy way which is based on Two Sum LeetCode problem in** O(n) time**.

    Here I have explained three optimal approaches to solve this problem. Two sum with hashmap or without hashmap.

    click here for the video explanation of generic algorithm with complexity analysis.

    or you can click on the image too to follow youtube tutorial.

    Here is the 100% working solution:-

    source code :

    // approach1- using hashmap
	static int[] icecreamParlorA1(int m, int[] arr) {
		int result[] = new int[2];
		Map<Integer, Integer> map = new HashMap<>();
		for (int i = 0; i < arr.length; i++) {
			int x = arr[i];
			int y = m - x;
			Integer j = map.get(y);
			if (j != null) {
				result[0] = j + 1;
				result[1] = i + 1;
				break;
			}
			map.put(x, i);

		}
		return result;
	}

	// approach2 - using array
	static int[] icecreamParlorA2(int m, int[] arr) {
		int result[] = new int[2];
		int n = arr.length;
		int frequency[] = new int[10001];

		Arrays.fill(frequency, -1);

		for (int i = 0; i < n; i++) {
			int x = arr[i];
			int y = m - x;

			if (y >= 0) {

				int j = frequency[y];

				if (j != -1) {
					result[0] = j + 1;
					result[1] = i + 1;
					break;
				}
			}

			frequency[x] = i;
		}

		return result;

	}

	// approach3- editorial approach with explanation
	static int[] icecreamParlorA3(int m, int[] arr) {
		int result[] = new int[2];
		int n = arr.length;
		int frequency[] = new int[10001];
		int firstFlavourIndex = 0;
		int secondFlavourIndexStartsFrom = 0;
		int secondFlavourCost = 0;

		for (int i = 0; i < n; i++) {
			int priceIndex = arr[i];
			frequency[priceIndex]++;
		}

		for (int i = 0; i < n; i++) {
			int firstFlavourCost = arr[i];
			frequency[firstFlavourCost]--;

			secondFlavourCost = m - firstFlavourCost;

			if (secondFlavourCost > 0 && frequency[secondFlavourCost] > 0) {
				firstFlavourIndex = i;
				secondFlavourIndexStartsFrom = firstFlavourIndex + 1;
				result[0] = firstFlavourIndex + 1;
				break;
			}

		}

		for (int i = secondFlavourIndexStartsFrom; i < n; i++) {
			if (arr[i] == secondFlavourCost) {
				result[1] = i + 1;
				break;
			}
		}

		return result;
	}

    Would really appreciate your feedback like, dislike , comment etc. on my video.

    Do not forget to upvote, if you find it useful.