StrangeCounter.c

#include <assert.h>
#include <ctype.h>
#include <limits.h>
#include <math.h>
#include <stdbool.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* readline();
char* ltrim(char*);
char* rtrim(char*);

long parse_long(char*);

/*
 * Complete the 'strangeCounter' function below.
 *
 * The function is expected to return a LONG_INTEGER.
 * The function accepts LONG_INTEGER t as parameter.
 */

long strangeCounter(long t) {
    long cycle_start = 1;  // Start time of the current cycle
    long cycle_length = 3; // Length of the first cycle

    // Find the cycle in which time "t" lies
    while (t >= cycle_start + cycle_length) {
        cycle_start += cycle_length;       // Move to the next cycle's start time
        cycle_length *= 2;                 // Each cycle's length doubles
    }

    // Calculate the value of the counter at time "t"
    long value_at_t = cycle_length - (t - cycle_start);
    return value_at_t;
}

int main()
{
    FILE* fptr = fopen(getenv("OUTPUT_PATH"), "w");

    long t = parse_long(ltrim(rtrim(readline())));

    long result = strangeCounter(t);

    fprintf(fptr, "%ld\n", result);

    fclose(fptr);

    return 0;
}

char* readline() {
    size_t alloc_length = 1024;
    size_t data_length = 0;

    char* data = malloc(alloc_length);

    while (true) {
        char* cursor = data + data_length;
        char* line = fgets(cursor, alloc_length - data_length, stdin);

        if (!line) {
            break;
        }

        data_length += strlen(cursor);

        if (data_length < alloc_length - 1 || data[data_length - 1] == '\n') {
            break;
        }

        alloc_length <<= 1;

        data = realloc(data, alloc_length);

        if (!data) {
            data = '\0';

            break;
        }
    }

    if (data[data_length - 1] == '\n') {
        data[data_length - 1] = '\0';

        data = realloc(data, data_length);

        if (!data) {
            data = '\0';
        }
    } else {
        data = realloc(data, data_length + 1);

        if (!data) {
            data = '\0';
        } else {
            data[data_length] = '\0';
        }
    }

    return data;
}

char* ltrim(char* str) {
    if (!str) {
        return '\0';
    }

    if (!*str) {
        return str;
    }

    while (*str != '\0' && isspace(*str)) {
        str++;
    }

    return str;
}

char* rtrim(char* str) {
    if (!str) {
        return '\0';
    }

    if (!*str) {
        return str;
    }

    char* end = str + strlen(str) - 1;

    while (end >= str && isspace(*end)) {
        end--;
    }

    *(end + 1) = '\0';

    return str;
}

long parse_long(char* str) {
    char* endptr;
    long value = strtol(str, &endptr, 10);

    if (endptr == str || *endptr != '\0') {
        exit(EXIT_FAILURE);
    }

    return value;
}