JetBrains Academy: Finding max and min in arrays - Kamil-Jankowski/Learning-JAVA GitHub Wiki

JetBrains Academy: Finding max and min in arrays

Find the max in an array:

Implement a method to find the max in an array of ints. The input arrays always contain at least one number.

public static int findMax(int[] numbers) {
    int max = numbers[0];
        
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] > max) {
            max = numbers[i];
        }
    }
        
    return max;
}

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Find the min in an array:

Implement a method to find the min in an array of ints. The input arrays always contain at least one number.

public static int findMin(int[] numbers) {
    int min = numbers[0];
        
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] < min) {
            min = numbers[i];
        }
    }
        
    return min;
}

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Find the index of the first min in an array:

Implement a method to find the index of the first min in an array of ints. If the input array is empty, the method should return -1.

public static int findIndexOfMin(int[] numbers) {
    if (numbers.length == 0) {
        return -1;
    }
        
    int minIndex = 0;
        
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] < numbers[minIndex]) {
            minIndex = i;
        }
    }
        
    return minIndex;
}

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Find index of the last max in an array:

Implement a method to find the index of the last max in an array of ints. If the input array is empty, the method should return -1.

public static int findIndexOfLastMax(int[] numbers) {
    if (numbers.length == 0) {
        return -1;
    }
       
    int lastMaxIndex = 0;
        
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] >= numbers[lastMaxIndex]) {
            lastMaxIndex = i;
        }
    }
        
    return lastMaxIndex;
}

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Find the index of K min in an array:

Implement a method that finds the index of the K-th element equal to the minimum in an array of ints. If no such element can be found, return -1. The input array can be empty, K > 0.

public static int findIndexOfKMin(int[] numbers, int k) {
    if (numbers.length == 0) {
        return -1;
    }
        
    int min = numbers[0];
    int indexOfKMin = -1;
    int counter = 0;
        
    //finding minimum value of the array
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] < min) {
            min = numbers[i];
        }
    }
    
    //finding minimum k-th element in the array
    for (int i = 0; i < numbers.length; i++) {
        if (numbers[i] == min) {
            counter++;
            if (counter == k) {
                indexOfKMin = i;
                break;
            }
        }
    }             
      
    return indexOfKMin;
}

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Find the second largest element in an array:

Implement a method to find the second largest number in an array of ints.

If the input array is empty or contains only a single number, the method must return Integer.MIN_VALUE.

If the input array contains multiple largest elements, consider them as the same value.

public static int findSecondLargestNumber(int[] numbers) {
    if (numbers.length <= 1) {
        return Integer.MIN_VALUE;
    }
        
    int max = numbers[0];
    int max2 = Integer.MIN_VALUE;
        
    for (int i = 1; i < numbers.length; i++) {
        if (numbers[i] > max) {
            max2 = max;
            max = numbers[i];
        } else if (numbers[i] == max) {
            continue;
        } else if (numbers[i] > max2) {
            max2 = numbers[i];
        }
    }
    
    return max2;
}

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