Adjacent Element Patterns in AP CSA

Many array algorithms compare or combine neighboring elements — arr[i] and arr[i+1]. The critical detail: your loop must stop one short of the last index to avoid an ArrayIndexOutOfBoundsException.

The Pattern

// Loop condition: i < arr.length - 1 (NOT i < arr.length)
for (int i = 0; i < arr.length - 1; i++) {
    // Now safe to access arr[i] AND arr[i+1]
    if (arr[i] > arr[i + 1]) {
        System.out.println("Drop at index " + i);
    }
}

Common Adjacent-Element Tasks

public static int mystery(int[] arr) {
    int count = 0;
    for (int i = 0; i < arr.length - 1; i++)
        if (arr[i] >= arr[i+1]) {
            count++;
        }
    return count;
}