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-rw-r--r--magnetic_force_2_balls.c43
1 files changed, 43 insertions, 0 deletions
diff --git a/magnetic_force_2_balls.c b/magnetic_force_2_balls.c
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+++ b/magnetic_force_2_balls.c
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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
+}