105 lines
2.9 KiB
C
105 lines
2.9 KiB
C
#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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// Finally a task that is favoring C
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#define BUFFER_SIZE 64
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#define MAX_LINES 8192
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// MIX_COUNT and DECRYPT_KEY is 1 for Part 1
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#define MIX_COUNT 10
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#define DECRYPT_KEY 811589153
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int main() {
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char buf[BUFFER_SIZE], *p, c;
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memset(buf, 0, BUFFER_SIZE);
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p = buf;
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long long lines[MAX_LINES], line_count = 0;
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while ((c = getchar()) != EOF) {
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*p++ = c;
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if (c == '\n') {
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sscanf(buf, "%lli", &lines[line_count]);
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lines[line_count] *= DECRYPT_KEY;
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line_count++;
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memset(buf, 0, BUFFER_SIZE);
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p = buf;
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}
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}
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// Create an array of pointers to keep track of the original order
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long long **order = (long long**)malloc(line_count * sizeof(long long*));
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for (int i = 0; i < line_count; i++) {
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order[i] = &lines[i];
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};
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long long *head = &lines[line_count-1];
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// Shuffle
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for (int ll = 0; ll < MIX_COUNT; ll++) {
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for (int i = 0; i < line_count; i++) {
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// Remove element from its original position
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long long element = *order[i];
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long long *q = order[i];
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while (q != head) {
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// Shift elements back
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*q = *(q+1);
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q++;
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}
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// Shift pointers
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for (int j = 0; j < line_count; j++) {
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if (order[j] > order[i]) {
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order[j]--;
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}
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}
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// Move where we need to insert
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order[i] += element;
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// Wrap around at the end
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// I don't get this wrapping logic that's in the example
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// it doesn't make any sense that I can not shift an element to the
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// last position because it already wraps to the first element
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if (order[i] > head) {
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order[i] = &lines[(order[i] - head) % (line_count-1)];
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} else if (order[i] <= lines) {
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order[i] = head - (lines - order[i]) % (line_count-1);
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}
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// Push every element back at insertion point
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q = head;
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while (q >= order[i] + 1) {
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// Shift elements
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*q = *(q-1);
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q--;
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}
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// Shift pointers
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for (int j = 0; j < line_count; j++) {
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if (order[j] >= order[i] && i != j) {
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order[j]++;
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}
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}
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// Insert element
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*order[i] = element;
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}
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}
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// Find 0
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long long *q = lines;
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while (*q != 0) { q++; }
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long long *th[3];
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th[0] = q + 1000;
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th[1] = q + 2000;
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th[2] = q + 3000;
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for (int i = 0; i < 3; i++) {
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if (th[i] > head) {
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th[i] = lines + ((th[i] - head) % line_count) - 1;
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}
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}
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printf("%lli\n", *(th[0])+*(th[1])+*(th[2]));
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free(order);
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}
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