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// 1552. Magnetic Force Between Two Balls
#include "leetcode.h"
/*
* in the universe earth c-137 rick discovered a special form of magnetic force
* between two balls if they are put in his new invented basket. rick has 'n'
* empty baskets the i'th basket is at 'position[i]', more has 'm' ball and
* needs to distribute the balls into the baskets such that the minimum magnetic
* force between any two balls is maximum. rick stated that magnetic force
* betweeen two different balls at positions 'x' and 'y' is '|x - y|'. given the
* integer array 'position' and the integer 'm', return the required force.
*/
int cmp(const void *a, const void *b) { return *(int *)a - *(int *)b; }
int cnt_ball(int *position, int positionSize, int distance) {
int cnt = 1, ptr = position[0];
for (int i = 1; i < positionSize; i++)
if (position[i] - ptr >= distance) {
ptr = position[i];
cnt++;
}
return cnt;
}
int maxDistance(int *position, int positionSize, int m) {
qsort(position, positionSize, sizeof(int), cmp);
int left = 1, right = position[positionSize - 1], mid;
while (left + 1 < right) {
mid = (left + right) / 2;
if (cnt_ball(position, positionSize, mid) >= m)
left = mid;
else
right = mid - 1;
}
return cnt_ball(position, positionSize, right) >= m ? right : left;
}
int main() {
int p1[] = {1, 2, 3, 4, 7}, p2[] = {5, 4, 3, 2, 1, 1000000000};
printf("%d\n", maxDistance(p1, ARRAY_SIZE(p1), 3)); // expect: 3
printf("%d\n", maxDistance(p2, ARRAY_SIZE(p2), 2)); // expect: 9999999
}
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