59. Scan Memory for Three Consecutive Increasing Values

#include <stdio.h>

int find_pattern(int *mem, int n) {
    if (n < 3) {
        return -1;
    }

    // init with first value
    int previous_value = *mem;
    int index_of_start = 0;

    // check with remaining values
    for (int i = 1; i < n; i++) {
        if (*(mem + i) == previous_value + 1) {
            // new item in sequence
            if (i == index_of_start + 2) {
                // we reached third element in sequence
                return index_of_start;
            }
        } else {
            // sequence break, start a new one
            index_of_start = i;
        }
        previous_value = *(mem + i);
    }
    return -1;
}

int main() {
    int n, arr[100];
    scanf("%d", &n);

    for (int i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }

    int res = find_pattern(arr, n);
    printf("%d", res);

    return 0;
}