添加 0151.翻转字符串里的单词.md Java版本

problems/0151.翻转字符串里的单词.md

@@ -212,6 +212,77 @@ public:
 
 
 Java：
+```java
+class Solution {
+  public String reverseWords(String s) {
+		char[] chars = s.toCharArray();
+		// 1.双指针去除空格
+		// 去除头尾空格
+		int head = 0;
+		while (chars[head] == ' ') {
+			head ++;
+		}
+		int tail = chars.length - 1;
+		while (chars[tail] == ' ') {
+			tail --;
+		}
+
+		// 去除中间空格
+		int p1 = head;
+		int p2 = head + 1;
+		while (p2 <= tail) {
+			if (chars[p2 -1] == ' ' && chars[p2] == ' ') {
+				p2 ++;
+				continue;
+			}
+			chars[p1 + 1] = chars[p2];
+			p1 ++;
+			p2 ++;
+		}
+
+		tail = p1;
+
+		// 2.双指针翻转整个字符串
+		chars = reverse(chars, head, tail);
+
+		// 3.双指针翻转每个单词
+		p1 = head;
+		p2 = head;
+
+		for (int i = head; i <= tail;) {
+			int add = 0;
+			while (i + add <= tail && chars[i + add] != ' ') {
+				add ++;
+			}
+
+			if (i + add != tail) {
+				reverse(chars, i, i + add - 1);
+				i += add + 1;
+			} else {
+				reverse(chars, i, tail);
+				i = tail + 1;
+			}
+		}
+
+		return new String(chars, head, tail - head + 1);
+  }
+
+  char[] reverse(char[] chars, int begin, int end) {
+		int p1 = begin;
+		int p2 = end;
+
+		while (p1 < p2) {
+			chars[p1] ^= chars[p2];
+			chars[p2] ^= chars[p1];
+			chars[p1] ^= chars[p2];
+
+			p1 ++;
+			p2 --;
+		}
+		return chars;
+	}
+}
+```
 
 
 Python：