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Diffstat (limited to 'longest_valid_course.c')
-rw-r--r-- | longest_valid_course.c | 67 |
1 files changed, 67 insertions, 0 deletions
diff --git a/longest_valid_course.c b/longest_valid_course.c new file mode 100644 index 0000000..893701b --- /dev/null +++ b/longest_valid_course.c @@ -0,0 +1,67 @@ +// 1964. Find the Longest Valid Obstacle Course at Each Position +#include "leetcode.h" + +/* + * you want to build obstacle courses. you are given a 0-indexed integer array + * 'obstacles' of length 'n' where 'obstacles[i]' describes the height of the + * i'th obstacle. for every index 'i' between 0 and 'n - 1' (inclusive), find + * the length of the longest obstacle course in 'obstacles' such that: + * - you choose any number of obstacles between 0 and 'i' inclusive + * - you must include the i'th obstacle in the course + * - you must put the chosen obstacles in the same order as they appear in + * 'obstacles' + * - every obstacle (except the first) is taller than or the same height as the + * obstacle immediately before it return an array 'ans' of length 'n', where + * 'ans[i]' is the length of the longest obstacle course for index 'i' as + * described above + */ + +int find(int *arr, int start, int end, int target) { + while (start < end) { + int mid = start + (end - start) / 2; + if (arr[mid] == target) + start = mid + 1; + else if (arr[mid] > target) + end = mid; + else + start = mid + 1; + } + return start; +} + +int *longestObstacleCourseAtEachPosition(int *obstacles, int obstaclesSize, + int *returnSize) { + int *ans = (int *)calloc(obstaclesSize, sizeof(int)); + int *cnt = (int *)calloc(obstaclesSize, sizeof(int)), n = 1; + ans[0] = 1; + cnt[0] = obstacles[0]; + for (int i = 1; i < obstaclesSize; i++) { + int idx = find(cnt, 0, n, obstacles[i]); + if (idx == n) + cnt[n++] = obstacles[i]; + else + cnt[idx] = obstacles[i]; + ans[i] = idx + 1; + } + *returnSize = obstaclesSize; + free(cnt); + return ans; +} + +int main() { + int o1[] = {1, 2, 3, 2}, o2[] = {2, 2, 1}, o3[] = {3, 1, 5, 6, 4, 2}, rs1, + rs2, rs3; + int *locaep1 = longestObstacleCourseAtEachPosition(o1, ARRAY_SIZE(o1), &rs1); + int *locaep2 = longestObstacleCourseAtEachPosition(o2, ARRAY_SIZE(o2), &rs2); + int *locaep3 = longestObstacleCourseAtEachPosition(o3, ARRAY_SIZE(o3), &rs3); + for (int i = 0; i < rs1; i++) + printf("%d ", locaep1[i]); // expect: 1 2 3 3 + printf("\n"); + for (int i = 0; i < rs2; i++) + printf("%d ", locaep2[i]); // expect: 1 2 1 + printf("\n"); + for (int i = 0; i < rs3; i++) + printf("%d ", locaep3[i]); // expect: 1 1 2 3 2 2 + printf("\n"); + free(locaep1), free(locaep2), free(locaep3); +} |