Valid anagram
# 思路：手动模拟hashtable，将字符串”a-z“的ASCII码作key，计数求差异
def isAnagram(self, s: str, t: str) -> bool:
arr1, arr2 = [0]*26, [0]*26
for i in s:
arr1[ord(i) - ord('a')] += 1
for i in t:
arr2[ord(i) - ord('a')] += 1
return arr1 == arr2
# 思路：map计数，对比计数差异
def isAnagram(self, s: str, t: str) -> bool:
dict1, dict2 = {}, {}
for item in s:
dict1[item] = dict1.get(item,0) + 1
for item in t:
dict2[item] = dict2.get(item,0) + 1
return dict1 == dict2
# 思路：数组排序后比较差异
def isAnagram(self, s: str, t: str) -> bool:
return sorted(s) == sorted(t)
public class Solution {
public boolean isAnagram(String s, String t) {
if(s.length() != t.length()) return false;
int [] a = new int [26];
for(Character c : s.toCharArray()) a[c - 'a']++;
for(Character c : t.toCharArray()) {
if(a[c -'a'] == 0) return false;
a[c - 'a']--;
}
return true;
}
}
public boolean isAnagram(String s1, String s2) {
int[] freq = new int[256];
for(int i = 0; i < s1.length(); i++) freq[s1.charAt(i)]++;
for(int i = 0; i < s2.length(); i++) if(--freq[s2.charAt(i)] < 0) return false;
return s1.length() == s2.length();
}
public boolean isAnagram(String s, String t)
{
char[] sChar = s.toCharArray();
char[] tChar = t.toCharArray();
Arrays.sort(sChar);
Arrays.sort(tChar);
return Arrays.equals(sChar, tChar);
}
Group Anagrams:
def groupAnagrams(self, strs):
d = {}
for w in sorted(strs):
key = tuple(sorted(w))
d[key] = d.get(key, []) + [w]
return d.values()
def groupAnagrams(self, strs):
dic = {}
for item in sorted(strs):
sortedItem = ''.join(sorted(item))
dic[sortedItem] = dic.get(sortedItem, []) + [item]
return dic.values()
public List<List<String>> groupAnagrams(String[] strs) {
List<List<String>> res = new ArrayList<>();
HashMap<String, List<String>> map = new HashMap<>();
Arrays.sort(strs);
for (int i = 0; i < strs.length; i++) {
String temp = strs[i];
char[] ch = temp.toCharArray();
Arrays.sort(ch);
if (map.containsKey(String.valueOf(ch))) {
map.get(String.valueOf(ch)).add(strs[i]);
} else {
List<String> each = new ArrayList<>();
each.add(strs[i]);
map.put(String.valueOf(ch), each);
}
}
for (List<String> item: map.values()) {
res.add(item);
}
return res;
}
Two sum
def twoSum(self, nums, target):
d = dict()
for index,num in enumerate(nums):
if d.get(num) == None:
d[target - num] = index
else:
return [d.get(num), index]
public int[] twoSum(int[] nums, int target) {
HashMap<Integer, Integer> tracker =
new HashMap<Integer, Integer>();
int len = nums.length;
for (int i = 0; i < len; i++){
if (tracker.containsKey(nums[i])){
int left = tracker.get(nums[i]);
return new int[]{left+1, i+1};
} else {
tracker.put(target - nums[i], i);
}
}
return new int[2];
}