Create LongestPalidromeSubstring.java

codewithcs · web-flow · commit 3126f4ae0b72 · 2020-05-06T15:41:39.000+01:00
diff --git a/Medium/LongestPalidromeSubstring.java b/Medium/LongestPalidromeSubstring.java
@@ -0,0 +1,55 @@
+class Program {
+		public static String longestPalindromicSubstring(String str) {
+
+		int maxLength = 0; int mid = -1; 
+		
+		for(int i=0 ; i<str.length()-1 ; i++){
+			
+			int oddLength = 0;
+			
+			if(i>0)
+			 oddLength = findPalindromeLength(str, i, i-1, i+1) +1; 
+			int evenLength = findPalindromeLength(str, i, i, i+1); 
+			
+			int currentLength = Math.max(oddLength, evenLength); 
+			
+			if(currentLength > maxLength){
+				mid = i; 
+				maxLength = currentLength ; 
+			}
+			
+		}
+	
+		boolean isOdd = (maxLength % 2 ) == 1 ;
+		
+		int maxLeft = isOdd ? mid - maxLength/2 : mid - maxLength/2 + 1 ;
+		
+		int maxRight = mid+maxLength/2; 
+		
+			if(maxLength == 0) {
+				return str ; 
+			}
+		return str.substring(maxLeft, maxRight+1); 
+		
+	}
+	
+	public static int findPalindromeLength (String str, int middle, int left, int right) {
+		int length = 0; 
+				
+		while(left >=0 && right <= str.length()-1) {
+		
+			if( str.charAt(left) == str.charAt(right) ) {
+				left-- ; 
+				right++ ;		
+				length = length + 2;
+			} else {
+				break; 
+			}
+		
+		}
+		
+		return length ; 
+		
+	}
+	
+}
