update: LC#557 added 2nd approach, reverse words in given string

Author: NirmalSilwal

Leetcode/MustDoEasyList/ReverseWordsInAStringIII557.java

@@ -1,5 +1,7 @@
 package MustDoEasyList;
 
+import java.util.Arrays;
+
 public class ReverseWordsInAStringIII557 {
 
 	public static String reverseWords(String s) {
@@ -30,7 +32,45 @@ private static String reverseOneWord(String word) {
 		return ans.toString();
 	}
 
+	// second approach
+	public static String reverseWords2(String s) {
+		int len = s.length();
+		char[] arr = s.toCharArray();
+
+		int firstidx = 0, lastidx = 0;
+
+		for (int i = 0; i < len; i++) {
+
+			if (arr[i] == ' ') {
+				lastidx = i - 1;
+				reverseHelper(arr, firstidx, lastidx);
+				firstidx = i + 1;
+			}
+		}
+
+		// now last word is left to be reversed
+		reverseHelper(arr, firstidx, len - 1);
+
+		return new String(arr);
+	}
+
+	private static void reverseHelper(char[] arr, int firstidx, int lastidx) {
+		while (firstidx < lastidx) {
+			char temp = arr[firstidx];
+			arr[firstidx] = arr[lastidx];
+			arr[lastidx] = temp;
+			firstidx++;
+			lastidx--;
+		}
+	}
+
 	public static void main(String[] args) {
-		System.out.println(reverseWords("hello world"));
+		System.out.println(reverseWords2("hello world"));
 	}
 }
+
+/*
+ * Input: s = "Let's take LeetCode contest"
+ * 
+ * Output: "s'teL ekat edoCteeL tsetnoc"
+ */