fix

haoyang.shi · haoyang.shi · commit cc8e3f78753d · 2019-05-08T14:56:48.000+08:00
diff --git a/offer/reConstructBinaryTree.md b/offer/reConstructBinaryTree.md
@@ -21,33 +21,19 @@ public TreeNode reConstructBinaryTree(int[] pre, int[] in) {
     return buildTree(preIndex, in, 0, in.length - 1);
 }
 
-private TreeNode buildTree(Map<Integer, Integer> preIndex,
-                           int[] in, int start, int end) {
-    Integer newRootValue = -1;
-    Integer newRootValueIndexInPre = Integer.MAX_VALUE;
-    for (int i = start; i <= end; i++) {
-        Integer cur = preIndex.get(in[i]);
-        if (cur < newRootValueIndexInPre) {
-            newRootValueIndexInPre = cur;
-            newRootValue = in[i];
-        }
+private TreeNode buildTree(Map<Integer, Integer> preIndex, int[] in, int start, int end) {
+    if (start == end) {
+        return new TreeNode(in[start]);
     }
-
-    Integer newRootValueIndexInIn = 0;
-    for (int i = 0; i < in.length; i++) {
-        if (newRootValue == in[i]) {
-            newRootValueIndexInIn = i;
+    int indexOfRoot = start;
+    for (int i = start; i <= end; i++) {
+        if (preIndex.get(in[i]) < preIndex.get(in[indexOfRoot])) {
+            indexOfRoot = i;
         }
     }
-
-    TreeNode root = new TreeNode(newRootValue);
-
-    if (start <= newRootValueIndexInIn - 1)
-        root.left = buildTree(preIndex, in, start, newRootValueIndexInIn - 1);
-
-    if (newRootValueIndexInIn + 1 <= end)
-        root.right = buildTree(preIndex, in, newRootValueIndexInIn + 1, end);
-
+    TreeNode root = new TreeNode(in[indexOfRoot]);
+    if (start <= indexOfRoot - 1) root.left = buildTree(preIndex, in, start, indexOfRoot - 1);
+    if (indexOfRoot + 1 <= end) root.right = buildTree(preIndex, in, indexOfRoot + 1, end);
     return root;
 }
 ```
diff --git a/offer/replay-space.md b/offer/replay-space.md
@@ -14,24 +14,11 @@
 ```
 public String replaceSpace(StringBuffer str) {
     char[] chars = str.toString().toCharArray();
-    int spaceCount = 0;
-
+    StringBuilder res = new StringBuilder();
     for (char c : chars) {
-        if (c == ' ') spaceCount++;
+        if (c == ' ') res.append("%20");
+        else res.append(c);
     }
-
-    char[] res = new char[chars.length + spaceCount * 2];
-
-    for (int i = 0, j = 0; i < chars.length; i++) {
-        if (chars[i] == ' ') {
-            res[j++] = '%';
-            res[j++] = '2';
-            res[j++] = '0';
-        } else {
-            res[j++] = chars[i];
-        }
-    }
-
-    return new String(res);
+    return res.toString();
 }
 ```
diff --git a/offer/two-stack-fifo.md b/offer/two-stack-fifo.md
@@ -2,7 +2,7 @@
 
 ## 题目
 
-https://www.nowcoder.com/practice/54275ddae22f475981afa2244dd448c6?tpId=13&tqId=11158&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking
+[牛客网](https://www.nowcoder.com/practice/54275ddae22f475981afa2244dd448c6?tpId=13&tqId=11158&rp=1&ru=/ta/coding-interviews&qru=/ta/coding-interviews/question-ranking)
 
 用两个栈来实现一个队列，完成队列的 Push 和 Pop 操作。 队列中的元素为int类型。
 
@@ -15,20 +15,20 @@ https://www.nowcoder.com/practice/54275ddae22f475981afa2244dd448c6?tpId=13&tqId=
 相当于将两个 stack 拼接：-> stack1 <::> stack2 ->
 
 ```
-Stack<Integer> stack1 = new Stack<>();
-Stack<Integer> stack2 = new Stack<>();
+Stack<Integer> pushStack = new Stack<>();
+Stack<Integer> popStack = new Stack<>();
 
 public void push(int node) {
-    stack1.push(node);
+    pushStack.push(node);
 }
 
 public int pop() {
-    if (stack2.isEmpty()) {
-        while (!stack1.isEmpty()) {
-            stack2.push(stack1.pop());
+    if (popStack.isEmpty()) {
+        while (!pushStack.isEmpty()) {
+            popStack.push(pushStack.pop());
         }
     }
-
-    return stack2.pop();
+    if (popStack.isEmpty()) return -1;
+    else return popStack.pop();
 }
 ```
