// 287. Find the Duplicate Number #include "leetcode.h" /* given an integer array 'nums' containing 'n + 1' integers where each integer * is in the range '[1, n]' inclusive. there is only one repeated number in * 'nums', return this repeated number. you must solve the problem without * modifying the array 'nums' and uses only constant extra space. */ int findDuplicate(int *nums, int nums_size) { int *cnt = (int *)calloc(nums_size, sizeof(int)); for (int i = 0; i < nums_size; i++) cnt[nums[i] - 1]++; for (int i = 0; i < nums_size; i++) if (cnt[i] >= 2) return i + 1; free(cnt); return -1; } int main() { int n1[] = {1, 3, 4, 2, 2}, n2[] = {3, 1, 3, 4, 2}; printf("%d\n", findDuplicate(n1, 5)); // expect: 2 printf("%d\n", findDuplicate(n2, 5)); // expect: 3 }