leetcode solution

705 Design HashSet Use BST tree to implement HashSet

349 Intersection of Two Arrays    (N) Sort both array nums1 and nums2 and call STL set_intersection to save result to nums1. create a set from nums1 beginning. create a vector of int out of the result set and return it. 242  Valid Anagram  (N) Solution 1： sort both the string s and t in ascending order. return s == t O(NlgN) time and O(1) space Solution 2: Use 2 hash map freq1 and freq2 to save the chars frequency of both s and t return the freq1 == freq2 350  Intersection of Two Arrays II        (Y) Solution 1: same with 349 Solution 2: Use hash Map to count the frequency of each number in the first array. In the second loop, loop each element in the second array, if freq[num]-- still > 0, add it to the result array, otherwise skip it. return the result array in the end. 524 Longest Word in Dictionary through Deleting     (Y)  Wihtout sorting: O((L + S) * D) = O(D(L + S)), O(L) space ...