init impl

Author: freemanzhang

src/string/FindAllAnagramsInAString.java

@@ -0,0 +1,89 @@
+package string;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+/*
+Given a string s and a non-empty string p, find all the start indices of p's anagrams in s.
+
+Strings consists of lowercase English letters only and the length of both strings s and p will not be larger than 20,100.
+
+The order of output does not matter.
+
+Example 1:
+
+Input:
+s: "cbaebabacd" p: "abc"
+
+Output:
+[0, 6]
+
+Explanation:
+The substring with start index = 0 is "cba", which is an anagram of "abc".
+The substring with start index = 6 is "bac", which is an anagram of "abc".
+Example 2:
+
+Input:
+s: "abab" p: "ab"
+
+Output:
+[0, 1, 2]
+
+Explanation:
+The substring with start index = 0 is "ab", which is an anagram of "ab".
+The substring with start index = 1 is "ba", which is an anagram of "ab".
+The substring with start index = 2 is "ab", which is an anagram of "ab".
+ * */
+
+public class FindAllAnagramsInAString
+{
+	public List<Integer> findAnagrams( String s, String p )
+	{
+		List<Integer> result = new ArrayList<>();
+		Map<Character, Integer> currWind = new HashMap<>();
+
+		for ( Character ch : p.toCharArray() )
+		{
+			currWind.put( ch, currWind.getOrDefault( ch, 0 ) + 1 );
+		}
+
+		int match = 0;
+		for ( int i = 0; i < s.length(); i++ )
+		{
+			// add char
+			char chToAdd = s.charAt( i );
+			if ( currWind.containsKey( chToAdd ) )
+			{
+				currWind.put( chToAdd, currWind.get( chToAdd ) - 1 );
+				if ( currWind.get( chToAdd ) == 0 )
+				{
+					match++;
+				}
+			}
+
+			// remove char
+			if ( i >= p.length() )
+			{
+				char chToRemove = s.charAt( i - p.length() );
+				if ( currWind.containsKey( chToRemove ) )
+				{
+					currWind.put( chToRemove, currWind.get( chToRemove ) + 1 );
+				}
+				if ( currWind.get( chToRemove ) == 1 )
+				{
+					match--;
+				}
+			}
+
+			// verify match
+			if ( match == currWind.size() )
+			{
+				result.add( i - p.length() + 1 );
+			}
+		}
+		
+		return result;
+	}
+}