151

Author: fay111101

…stack/EvaluateReversePolishNotation.java …/_150_EvaluateReversePolishNotation.javasrc/main/java/leetcode/stack/EvaluateReversePolishNotation.java renamed to src/main/java/leetcode/stack/_150_EvaluateReversePolishNotation.java src/main/java/leetcode/stack/EvaluateReversePolishNotation.java renamed to src/main/java/leetcode/stack/_150_EvaluateReversePolishNotation.java

@@ -2,12 +2,40 @@
 
 import java.util.Stack;
 
-/*Evaluate the value of an arithmetic expression in Reverse Polish Notation.
-Valid operators are+,-,*,/. Each operand may be an integer or another expression.
-Some examples:
-  ["2", "1", "+", "3", "*"] -> ((2 + 1) * 3) -> 9
-  ["4", "13", "5", "/", "+"] -> (4 + (13 / 5)) -> 6*/
-public class EvaluateReversePolishNotation {
+/**
+ * 根据逆波兰表示法，求表达式的值。
+ *
+ * 有效的运算符包括 +, -, *, / 。每个运算对象可以是整数，也可以是另一个逆波兰表达式。
+ *
+ * 说明：
+ *
+ * 整数除法只保留整数部分。
+ * 给定逆波兰表达式总是有效的。换句话说，表达式总会得出有效数值且不存在除数为 0 的情况。
+ * 示例 1：
+ *
+ * 输入: ["2", "1", "+", "3", "*"]
+ * 输出: 9
+ * 解释: ((2 + 1) * 3) = 9
+ * 示例 2：
+ *
+ * 输入: ["4", "13", "5", "/", "+"]
+ * 输出: 6
+ * 解释: (4 + (13 / 5)) = 6
+ * 示例 3：
+ *
+ * 输入: ["10", "6", "9", "3", "+", "-11", "*", "/", "*", "17", "+", "5", "+"]
+ * 输出: 22
+ * 解释:
+ *   ((10 * (6 / ((9 + 3) * -11))) + 17) + 5
+ * = ((10 * (6 / (12 * -11))) + 17) + 5
+ * = ((10 * (6 / -132)) + 17) + 5
+ * = ((10 * 0) + 17) + 5
+ * = (0 + 17) + 5
+ * = 17 + 5
+ * = 22
+ */
+public class _150_EvaluateReversePolishNotation {
+
     public int evalRPN(String[] tokens) {
 
         Stack<Integer> stack=new Stack<>();
@@ -45,7 +73,7 @@ public int operation(String token,int a,int b){
     }
     public static void main(String[] args){
         String[] arr={"2", "1", "+", "3", "*"};
-        EvaluateReversePolishNotation test=new EvaluateReversePolishNotation();
+        _150_EvaluateReversePolishNotation test=new _150_EvaluateReversePolishNotation();
         System.out.println(test.evalRPN(arr));
 
     }

src/main/java/leetcode/string/_151_ReverseWords.java

@@ -0,0 +1,96 @@
+package leetcode.string;
+
+/**
+ *
+ */
+public class _151_ReverseWords {
+
+    public String reverseWords(String s) {
+        if (s == null )
+            return s;
+        if(s.trim().length()==0){
+            return s.trim();
+        }
+        char[] arr = s.toCharArray();
+        int left = 0, right = s.length() - 1;
+        // 完全翻转
+        reverse(arr,left,right);
+        //翻转单个单词
+        reverseWord(arr);
+        //空格处理
+        return cleanSpaces(arr);
+    }
+
+    private String cleanSpaces(char[] arr) {
+        int n=arr.length;
+        int i=0,j=0;
+        while(j<n){
+            while(j<n&&arr[j]==' ')
+                j++;
+            while(j<n&&arr[j]!=' '){
+                arr[i++]=arr[j++];
+            }
+            while(j<n&&arr[j]==' ')
+                j++;
+            if(j<n)
+                arr[i++]=' ';
+        }
+        return new String(arr).substring(0,i);
+    }
+
+    private void reverseWord(char[] arr) {
+        int n=arr.length,i=0,j=0;
+        while(j<n){
+            while(i<j||i<n&&arr[i]==' ')
+                i++;
+            while(j<i||j<n&&arr[j]!=' ')
+                j++;
+            reverse(arr,i,j-1);
+        }
+    }
+    //翻转left到right间的字母
+    private void reverse(char[] arr, int left, int right) {
+        while(left<right){
+            char temp=arr[left];
+            arr[left]=arr[right];
+            arr[right]=temp;
+            left++;
+            right--;
+        }
+    }
+
+
+    public String reverseWords1(String s) {
+
+        char[] array = s.toCharArray();
+        if (array.length == 0)
+            return s;
+        char[] res = new char[array.length];
+        int len = helper(array, array.length - 1, res, 0, 0);
+        return new String(res, 0, len);
+
+    }
+
+    private int helper(char[] array, int r, char[] res, int l, int len) {
+        while (r >= 0 && array[r] == ' ')
+            r--;
+        if (r < 0)
+            return Math.max(0, len - 1);
+        int right = r;
+        while (r >= 0 && array[r] != ' ')
+            r--;
+        len += right - r + 1;
+        for (int left = r + 1; left <= right; left++, l++)
+            res[l] = array[left];
+        if (l < res.length)
+            res[l++] = ' ';
+        return helper(array, r, res, l, len);
+    }
+
+    public static void main(String[] args) {
+        String s=" 1";
+        _151_ReverseWords test=new _151_ReverseWords();
+        System.out.println(test.reverseWords(s));
+
+    }
+}