230 lines
7.5 KiB
C
230 lines
7.5 KiB
C
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <limits.h>
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#define BUFFER_SIZE 128
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#define MAX_SENSORS 128
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#define MAX_RANGES 128
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#define Y_ROW 2000000L
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#define MIN_YPOS 0L
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#define MAX_YPOS 4000000L
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#define XTUNING 4000000ULL
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#define max(a,b) (a >= b ? a : b)
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#define min(a,b) (a <= b ? a : b)
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#define abs(v) ((v) < 0 ? (-1) * (v) : (v))
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typedef struct sensor {
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long x;
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long y;
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long beaconX;
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long beaconY;
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long radius;
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} SENSOR;
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long dist(long, long, long, long);
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int exists(long [], int, long);
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unsigned overlap(long, long, long, long);
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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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SENSOR sensors[MAX_SENSORS], tmp;
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int sensor_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, "Sensor at x=%li, y=%li: closest beacon is at x=%li, y=%li", &tmp.x, &tmp.y, &tmp.beaconX, &tmp.beaconY);
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tmp.radius = dist(tmp.x, tmp.y, tmp.beaconX, tmp.beaconY);
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sensors[sensor_count] = tmp;
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sensor_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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// Scan every row in the given territory
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for (long jk = MIN_YPOS; jk < MAX_YPOS; jk++) {
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// Save the range for each sensor
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long (*scanned)[2];
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scanned = (long(*)[2])malloc(sensor_count * sizeof(long[2]));
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memset(scanned, 0, sensor_count * sizeof(long[2]));
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unsigned sum = 0;
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// Find all scanned in y=jk
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for (int i = 0; i < sensor_count; i++) {
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// Not in range
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if (abs(sensors[i].y - jk) > sensors[i].radius) {
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continue;
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}
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unsigned tmp = (sensors[i].radius - abs(sensors[i].y - jk));
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scanned[i][0] = sensors[i].x - tmp;
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scanned[i][1] = sensors[i].x + tmp;
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}
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long (*ranges)[2];
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ranges = (long(*)[2])malloc(MAX_RANGES * sizeof(long[2]));
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memset(ranges, 0, MAX_RANGES * sizeof(long[2]));
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int range_count = 0;
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// Count scanned and remove overlaps
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for (int i = 0; i < sensor_count; i++) {
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long sections[16][2];
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int section_count = 0;
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sections[0][0] = scanned[i][0];
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sections[0][1] = scanned[i][1];
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section_count++;
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for (int j = 0; j < range_count; j++) {
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for (int k = 0; k < section_count; k++) {
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// Not overlapping
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if (sections[k][0] > ranges[j][1] || sections[k][1] < ranges[j][0]) {
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continue;
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}
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// fully covered
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else if (sections[k][0] >= ranges[j][0] && sections[k][1] <= ranges[j][1]) {
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for (int l = k; l < section_count - 1; l++) {
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sections[l][0] = sections[l+1][0];
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sections[l][1] = sections[l+1][1];
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}
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section_count--;
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break;
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}
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// Inverse covered splits section to two
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else if (sections[k][0] < ranges[j][0] && sections[k][1] > ranges[j][1]) {
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// Push everything forward
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for (int l = section_count; l > k + 1; l--) {
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sections[l][0] = sections[l-1][0];
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sections[l][1] = sections[l-1][1];
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}
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section_count++;
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sections[k+1][1] = sections[k][1];
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sections[k][1] = ranges[j][0] - 1;
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sections[k+1][0] = ranges[j][1] + 1;
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}
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// Left hook
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else if (sections[k][0] < ranges[j][0] && sections[k][1] <= ranges[j][1]) {
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sections[k][1] = ranges[j][0] - 1;
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}
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// Right hook
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else if (sections[k][0] >= ranges[j][0] && sections[k][1] > ranges[j][1]) {
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sections[k][0] = ranges[j][1] + 1;
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}
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}
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}
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for (int j = 0; j < section_count; j++) {
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ranges[range_count][0] = sections[j][0];
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ranges[range_count][1] = sections[j][1];
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range_count++;
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}
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}
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//printf("OPOPOP\n");
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int changeCount = 0;
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// Combine ranges
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do {
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changeCount = 0;
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for (int i = 0; i < range_count; i++) {
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for (int j = i + 1; j < range_count; j++) {
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if (ranges[i][0] == ranges[j][1] + 1) {
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ranges[i][0] = ranges[j][0];
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for (int k = j; k < range_count - 1; k++) {
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ranges[k][0] = ranges[k+1][0];
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ranges[k][1] = ranges[k+1][1];
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}
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range_count--;
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changeCount++;
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} else if (ranges[i][1] + 1 == ranges[j][0]) {
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ranges[i][1] = ranges[j][1];
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for (int k = j; k < range_count - 1; k++) {
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ranges[k][0] = ranges[k+1][0];
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ranges[k][1] = ranges[k+1][1];
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}
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range_count--;
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changeCount++;
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}
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}
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}
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} while (changeCount != 0);
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for (int i = 0; i < range_count; i++) {
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//printf("[%li,%li]\n", ranges[i][0], ranges[i][1]);
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sum += ranges[i][1] - ranges[i][0] + 1;
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}
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// I don't really understand why, but we also have to exclude beacons
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long beaconInWay[32];
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int beaconInWayCount = 0;
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for (int i = 0; i < sensor_count; i++) {
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int skip = 0;
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if (sensors[i].beaconY != jk) {
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continue;
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}
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for (int k = 0; k < beaconInWayCount; k++) {
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if (beaconInWay[k] == sensors[i].beaconX) {
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skip = 1;
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break;
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}
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}
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if (skip) {
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continue;
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}
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for (int j = 0; j < range_count; j++) {
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if (sensors[i].beaconX >= ranges[j][0] && sensors[i].beaconX <= ranges[j][1]) {
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beaconInWay[beaconInWayCount] = sensors[i].beaconX;
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beaconInWayCount++;
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sum -= 1;
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}
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}
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}
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// Finally print the results
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if (jk == Y_ROW) {
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printf("Part one: %u\n", sum);
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}
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// Second part
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for (int i = 0; i < range_count; i++) {
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if (ranges[i][0] > MIN_YPOS && ranges[i][0] <= MAX_YPOS) {
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printf("X: %li, Y: %li\n", ranges[i][0] - 1, jk);
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printf("Second part: %llu\n", (unsigned long long)(ranges[i][0]-1)*XTUNING+(unsigned long long)jk);
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}
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}
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free(scanned);
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free(ranges);
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}
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}
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long dist(long x1, long y1, long x2, long y2) {
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return abs(x1-x2) + abs(y1-y2);
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}
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// We could do better if we want speed
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// But I hope it is enough
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int exists(long scanned[], int scanned_count, long x) {
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for (int i = 0; i < scanned_count; i++) {
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if (scanned[i] == x) {
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return 1;
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}
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}
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return 0;
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}
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unsigned overlap(long min1, long max1, long min2, long max2) {
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if (max1 < min2 || max2 < min1)
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return 0;
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return min(max1, max2) - max(min1, min2) + 1;
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}
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