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// 2751. Robot Collisions
#include "leetcode.h"
/*
* there are 'n' 1 indexed robots, each having a position on a line, health, and
* movement directions. all robots start moving on the line simultaneously at
* the same speed in their given directions. if two robots ever share the same
* position while moving, they will collide. if two robots collide, the robot
* with lower health is removed from the line and the health of the other robot
* decreases by 1. the surviving robot continues in the same direction it was
* going. if both robots have the same health they are both removed from the
* line. return an array containing the health of the remaining robots after no
* further collisions can occur
*/
int cmp(const void *a, const void *b) {
int *aa = *(int **)a, *bb = *(int **)b;
return aa[0] - bb[0];
}
int *survivedRobotsHealths(int *positions, int positionsSize, int *healths,
int healthsSize, char *directions, int *returnSize) {
int **record = (int **)malloc(sizeof(int *) * positionsSize);
int *stack = (int *)malloc(sizeof(int) * positionsSize), idx = -1;
int *ans = (int *)malloc(sizeof(int) * positionsSize);
*returnSize = 0;
for (int i = 0; i < positionsSize; i++) {
record[i] = (int *)malloc(sizeof(int) * 2);
record[i][0] = positions[i];
record[i][1] = i;
if (directions[i] == 'L')
healths[i] *= 1;
}
qsort(record, positionsSize, sizeof(int *), cmp);
for (int i = 0; i < positionsSize; i++) {
if (idx == -1) {
stack[++idx] = record[i][1];
} else if (healths[record[i][1]] < 0 && healths[stack[idx]] > 0) {
if (healths[stack[idx]] == -1 * healths[record[i][1]]) {
healths[stack[idx]] = 0;
healths[record[i][1]] = 0;
idx--;
} else if (healths[stack[idx]] > -1 * healths[record[i][1]]) {
healths[record[i][1]] = 0;
healths[stack[idx]] -= 1;
} else {
while (idx != -1 && healths[stack[idx]] > 0 &&
healths[stack[idx]] < -1 * healths[record[i][1]]) {
healths[stack[idx]] = 0;
idx--;
healths[record[i][1]] += 1;
}
if (idx == -1 || healths[stack[idx]] < 0) {
stack[++idx] = record[i][1];
} else if (-1 * healths[record[i][1]] == healths[stack[idx]]) {
healths[stack[idx]] = 0;
healths[record[i][1]] = 0;
idx--;
} else {
healths[record[i][1]] = 0;
healths[stack[idx]] -= 1;
}
}
} else {
stack[++idx] = record[i][1];
}
}
for (int i = 0; i < positionsSize; i++)
free(record[i]);
free(record), free(stack);
for (int i = 0; i < positionsSize; i++)
if (healths[i])
ans[(*returnSize)++] = abs(healths[i]);
return ans;
}
int main() {
int p1[] = {5, 4, 3, 2, 1}, h1[] = {2, 17, 9, 15, 10}, rs1;
int p2[] = {3, 5, 2, 6}, h2[] = {10, 10, 15, 12}, rs2;
int p3[] = {1, 2, 5, 6}, h3[] = {10, 10, 11, 11}, rs3;
char s1[] = "RRRRR", s2[] = "RLRL", s3[] = "RLRL";
int *sbh1 =
survivedRobotsHealths(p1, ARRAY_SIZE(p1), h1, ARRAY_SIZE(h1), s1, &rs1);
int *sbh2 =
survivedRobotsHealths(p2, ARRAY_SIZE(p2), h2, ARRAY_SIZE(h2), s2, &rs2);
int *sbh3 =
survivedRobotsHealths(p3, ARRAY_SIZE(p3), h3, ARRAY_SIZE(h3), s3, &rs3);
for (int i = 0; i < rs1; i++)
printf("%d ", sbh1[i]); // expect: 2,17,9,15,10
printf("\n");
for (int i = 0; i < rs2; i++)
printf("%d ", sbh2[i]); // expect: 14
printf("\n");
for (int i = 0; i < rs3; i++)
printf("%d ", sbh3[i]); // expect: null
printf("\n");
free(sbh1), free(sbh2), free(sbh3);
}
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