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Linear search is a very simple algorithm. In this type of search, sequential search is made over all items one by one.

Every item is checked and if a match is found then that particular item is returned, otherwise search will continue till the end of the data collection.

Let's start coding for linear search

package com.praveen.search.linear;

public class LinearSearch {

	public static void main(String[] args) {
		int[] arr = { 90, 24, 46, 35, 32 };
		System.out.println(search(arr, 32));
		System.out.println(search(arr, 46));
		System.out.println(search(arr, 100));

	}

	private static int search(int[] arr, int target) {

		for (int i = 0; i < arr.length; i++) {
			if (arr[i] == target) {
				return i;
			}
		}
		return -1;

	}

}

Output

4
2
-1

Let's see some programs

1. Search in Range

package com.praveen.search.linear;

public class SearchInRange {

	public static void main(String[] args) {
		int[] arr = { 90, 24, 46, 35, 32 };
		System.out.println(searchInRange(arr, 32, 1, 3));
		System.out.println(searchInRange(arr, 46, 1, 3));

	}

	private static int searchInRange(int[] arr, int target, int start, int end) {
		for (int i = start; i <= end; i++) {
			if (arr[i] == target) {
				return i;
			}
		}
		return -1;
	}

}

Output

-1
2

2. Find minimum element in an array

package com.praveen.search.linear;

public class FindMin {

	public static void main(String[] args) {
		int[] arr = { 90, 24, 46, 35, 32 };
		System.out.println(min(arr));
	}

	private static int min(int[] arr) {
		int min = arr[0];
		for (int i : arr) {
			if (i < min) {
				min = i;
			}
		}
		return min;
	}

}

Output

24

3. Search in 2D Array

package com.praveen.search.linear;

import java.util.Arrays;

public class SearchIn2DArray {

	public static void main(String[] args) {

		int[][] arr = { { 12, 18, 21 }, { 89, 73, 23, 92 }, { 6, 32, 1 }, { 10, 43 } };

		System.out.println(Arrays.toString(searchIn2DArray(arr, 32)));
		System.out.println(Arrays.toString(searchIn2DArray(arr, 43)));
		System.out.println(Arrays.toString(searchIn2DArray(arr, 73)));
		System.out.println(Arrays.toString(searchIn2DArray(arr, 100)));

	}

	private static int[] searchIn2DArray(int[][] arr, int target) {

		for (int row = 0; row < arr.length; row++) {
			for (int col = 0; col < arr[row].length; col++) {

				if (target == arr[row][col]) {
					return new int[] { row, col };
				}
			}
		}

		return new int[] { -1, -1 };

	}

}

Output

[2, 1]
[3, 1]
[1, 1]
[-1, -1]

4. Maximum value in 2D Array

package com.praveen.search.linear;

public class FindMaxin2DArray {

	public static void main(String[] args) {
		int[][] arr = { { 12, 18, 21 }, { 89, 73, 23, 92 }, { 6, 32, 1 }, { 10, 43 } };

		System.out.println(maxIn2DArray(arr));

	}

	private static int maxIn2DArray(int[][] arr) {

		int max = Integer.MIN_VALUE;

		for (int row = 0; row < arr.length; row++) {
			for (int col = 0; col < arr[row].length; col++) {

				if (arr[row][col] > max) {
					max = arr[row][col];
				}
			}
		}

		return max;

	}

}

Output

92

5. Find numbers with even number of digits

package com.praveen.search.linear;

public class FindEvenNumberOfDigits {

	public static void main(String[] args) {
		System.out.println(findNumbers(new int[] { 12, 345, 2, 6, 7896 }));
		System.out.println(findNumbers(new int[] { 92, 122, 9062, 230455, -36533 }));
		System.out.println(findNumbers(new int[] { 0, 12, 312, 9765, 12345 }));
	}

	private static int findNumbers(int[] arr) {
		int count = 0;
		for (int i : arr) {
			if (even(i)) {
				count++;
			}
		}
		return count;

	}

	private static boolean even(int num) {

		return digits(num) % 2 == 0;
	}

	private static int digits(int num) {

		if (num < 0) {
			num *= -1;
		}

		if (num == 0) {
			num = 1;
		}

		return (int) (Math.log10(num) + 1);
	}

}

Output

2
3
2

6. Richest Customer Wealth

package com.praveen.search.linear;

public class MaximumWealth {

	public static void main(String[] args) {

		System.out.println(maximumWealth(new int[][] { { 1, 2, 3 }, { 3, 2, 1 } }));
		System.out.println(maximumWealth(new int[][] { { 1, 6, 3 }, { 9, 8, 4 }, { 12, 1, 0 } }));
		System.out.println(maximumWealth(new int[][] { { 11, 32, 53 }, { 29, 38, 24 }, { 112, -1, 10 } }));

	}

	private static int maximumWealth(int[][] accounts) {

		int sum = 0;
		int max = Integer.MIN_VALUE;

		for (int[] ints : accounts) {
			sum = 0;
			for (int elements : ints) {
				sum += elements;
			}

			if (sum > max) {
				max = sum;
			}

		}

		return max;

	}

}

Output

6
21
121