栈和队列

Author: da183

Diff for: data_structure/stack_queue.md

@@ -69,39 +69,42 @@ public:
 思路：通过栈保存原来的元素，遇到表达式弹出运算，再推入结果，重复这个过程
 
 ```c++
-int evalRPN(vector<string> &tokens) {
-   if (tokens.empty()) {
-        return 0;
-    }
-    auto token = tokens.back();
-    tokens.pop_back();
-    if (token != "+" && token != "-" && token != "*" && token != "/") {
-        return atoi(token);
-    }
-    auto rhs = evalRPN(tokens);
-    auto lhs = evalRPN(tokens);
-    if (token == "+") {
-        return lhs + rhs;
-    } else if (token == "-") {
-        return lhs - rhs;
-    } else if (token == "*") {
-        return lhs * rhs;
-    } else if (token == "/") {
-        return lhs / rhs;
-    }
-    return -1;
-}
-
-int atoi(const string &str) {
-    if (str[0] == '-') {
-        return -atoi(str.substr(1));
+class Solution {
+public:
+    int evalRPN(vector<string> &tokens) {
+       if (tokens.empty()) {
+            return 0;
+        }
+        auto token = tokens.back();
+        tokens.pop_back();
+        if (token != "+" && token != "-" && token != "*" && token != "/") {
+            return atoi(token);
+        }
+        auto rhs = evalRPN(tokens);
+        auto lhs = evalRPN(tokens);
+        if (token == "+") {
+            return lhs + rhs;
+        } else if (token == "-") {
+            return lhs - rhs;
+        } else if (token == "*") {
+            return lhs * rhs;
+        } else if (token == "/") {
+            return lhs / rhs;
+        }
+        return -1;
     }
-    int ret = 0;
-    for (const auto &item : str) {
-        ret = ret * 10 + item - '0';
+
+    int atoi(const string &str) {
+        if (str[0] == '-') {
+            return -atoi(str.substr(1));
+        }
+        int ret = 0;
+        for (const auto &item : str) {
+            ret = ret * 10 + item - '0';
+        }
+        return ret;
     }
-    return ret;
-}
+};
 ```
 
 [decode-string](https://leetcode-cn.com/problems/decode-string/)
@@ -114,57 +117,60 @@ int atoi(const string &str) {
 思路：通过栈辅助进行操作
 
 ```c++
+class Solution {
+public:
 string decodeString(string s) {
-    if (s.empty()) {
-        return "";
-    }
-
-    vector<char> stack;
-    for (const auto &c : s) {
-        if (c != ']') {
-            stack.push_back(c);
-            continue;
+        if (s.empty()) {
+            return "";
         }
-        vector<char> subStr;
-        while (stack.back() != '[') {
-            subStr.push_back(stack.back());
+
+        vector<char> stack;
+        for (const auto &c : s) {
+            if (c != ']') {
+                stack.push_back(c);
+                continue;
+            }
+            vector<char> subStr;
+            while (stack.back() != '[') {
+                subStr.push_back(stack.back());
+                stack.pop_back();
+            }
             stack.pop_back();
-        }
-        stack.pop_back();
 
-        int digitBegin = stack.size() - 1;
-        for (; digitBegin != 0; --digitBegin) {
-            auto val = stack[digitBegin];
-            if (!('0' <= val && val <= '9')) {
-                ++digitBegin;
-                break;
+            int digitBegin = stack.size() - 1;
+            for (; digitBegin != 0; --digitBegin) {
+                auto val = stack[digitBegin];
+                if (!('0' <= val && val <= '9')) {
+                    ++digitBegin;
+                    break;
+                }
+            }
+            auto repeat = atoi({
+                                    stack.begin() + digitBegin,
+                                    stack.end(),
+                            });
+            stack.resize(digitBegin);
+            for (int i = 0; i < repeat; ++i) {
+                stack.insert(stack.end(), subStr.rbegin(), subStr.rend());
             }
         }
-        auto repeat = atoi({
-                                stack.begin() + digitBegin,
-                                stack.end(),
-                        });
-        stack.resize(digitBegin);
-        for (int i = 0; i < repeat; ++i) {
-            stack.insert(stack.end(), subStr.rbegin(), subStr.rend());
-        }
+        return {
+            stack.begin(),
+            stack.end()
+        };
     }
-    return {
-        stack.begin(),
-        stack.end()
-    };
-}
 
-int atoi(const string &str) {
-    if (str.empty()) {
-        return 0;
-    }
-    int value = 0;
-    for (const auto &c : str) {
-        value = value * 10 + c - '0';
+    int atoi(const string &str) {
+        if (str.empty()) {
+            return 0;
+        }
+        int value = 0;
+        for (const auto &c : str) {
+            value = value * 10 + c - '0';
+        }
+        return value;
     }
-    return value;
-}
+};
 ```
 
 利用栈进行 DFS 递归搜索模板