46. Detect Alternating Pattern

#include <stdio.h>

int is_alternating_pattern(int *mem, int k) {
    int *curr = mem;
    int expected = *curr;  // starting value: either 0 or 1

    for (int i = 0; i < k; i++) {
        if (*curr != expected) {
            return 0;
        }
        expected = 1 - expected;  // alternate expectation
        curr++;  // move pointer forward
    }
    return 1;
}

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

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

    int res = is_alternating_pattern(arr, k);
    printf("%d", res);

    return 0;
}

Pattern detection is critical in memory validation, UART bitstreams, and protocol framing. This simulates the validation logic of expected alternating signals.

Solution Logic:

• Start with the first element’s value as the expected pattern
• Walk the pointer forward
• On each step, compare the value with the expected
• Flip expected between 1 and 0
• If all match → return 1; otherwise, return 0
   

Alternate Logic

int is_alternating_pattern(int *mem, int k) {
    for (int i = 0; i < k; i++) {
        if (*(mem + i) != (i % 2 == 0 ? *mem : 1 - *mem)) {
            return 0;
        }
    }
    return 1;
}