find all anagrams in a string

Author: fishercoder1534

EASY/src/easy/FindAllAnagramsinaString.java

@@ -0,0 +1,64 @@
+package easy;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class FindAllAnagramsinaString {
+    /**O(m*n) solution, my original and most intuitive one, but kind of brute force.*/
+    public List<Integer> findAnagrams(String s, String p) {
+        List<Integer> result = new ArrayList();
+        for (int i = 0; i <= s.length()-p.length(); i++){
+            if (isAnagram(s.substring(i, i+p.length()), p)) result.add(i);
+        }
+        return result;
+    }
+    
+    private boolean isAnagram(String s, String p){
+        int[] c = new int[26];
+        for (int i = 0; i < s.length(); i++){
+            c[s.charAt(i) - 'a']++;
+            c[p.charAt(i) - 'a']--;
+        }
+        
+        for (int i : c){
+            if(i != 0) return false;
+        }
+        return true;
+    }
+
+    
+    static class SlidingWindowSolution {
+        /**O(n) solution inspired by this post: https://discuss.leetcode.com/topic/64434/shortest-concise-java-o-n-sliding-window-solution*/
+        public List<Integer> findAnagrams(String s, String p) {
+            List<Integer> result = new ArrayList();
+            int[] hash = new int[26];
+            for (char c : p.toCharArray()){
+                hash[c - 'a']++;
+            }
+            int start = 0, end = 0, count = p.length();
+            while (end < s.length()){
+                if(hash[s.charAt(end) - 'a'] > 0){
+                    count--;
+                }
+                hash[s.charAt(end) - 'a']--;
+                end++;
+                
+                if(count == 0) result.add(start);
+                
+                if((end - start) == p.length()){
+                    if(hash[s.charAt(start) - 'a'] >= 0) count++;
+                    hash[s.charAt(start) - 'a']++;
+                    start++;
+                }
+            }
+            return result;
+        }
+    }
+    
+    public static void main(String...args){
+        SlidingWindowSolution test = new SlidingWindowSolution();
+        String s = "cbaebabacd";
+        String p = "abc";
+        test.findAnagrams(s, p);
+    }
+}

README.md

@@ -5,6 +5,7 @@
 |453|[Minimum Moves to Equal Array Elements](https://leetcode.com/problems/minimum-moves-to-equal-array-elements/)|[Solution](../../blob/master/EASY/src/easy/MinimumMovestoEqualArrayElements.java)| O(n)|O(1) | Easy|
 |447|[Number of Boomerangs](https://leetcode.com/problems/number-of-boomerangs/)|[Solution](../../blob/master/EASY/src/easy/NumberofBoomerangs.java)| O(n^2)|O(n) | Easy| HashMap
 |441|[Arranging Coins](https://leetcode.com/problems/arrange-coins/)|[Solution](../../blob/master/EASY/src/easy/ArrangingCoins.java)| O(n)|O(1) | Easy|
+|438|[Find All Anagrams in a String](https://leetcode.com/problems/find-all-anagrams-in-a-string/)|[Solution](../../blob/master/EASY/src/easy/FindAllAnagramsinaString.java)| O(n)|O(1) | Easy|
 |436|[Find Right Interval](https://leetcode.com/problems/find-right-interval/)|[Solution](../../blob/master/MEDIUM/src/medium/FindRightInterval.java) | O(nlogn) |O(n) | Medium| Binary Search
 |435|[Non-overlapping Intervals](https://leetcode.com/problems/non-overlapping-intervals/)|[Solution](../../blob/master/MEDIUM/src/medium/NonOverlappingIntervals.java) | O(nlogn) |O(1) | Medium| Greedy
 |420|[Strong Password Checker](https://leetcode.com/problems/strong-password-checker/)|[Solution](../../blob/master/HARD/src/hard/StrongPasswordChecker.java)| ? | ? | Hard|