'commit'

TangDou/CSP-J/J2_2020/ZhuanTi_BiaoDaShi/ToPostFix/PrefixToPostfix_WithBlank.cpp

@@ -0,0 +1,45 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+/*
+测试样例：
++ 23 34
+
+/ + 4 2 * 3 5
+*/
+
+// 将前缀表达式转换为后缀表达式(带空格版本)
+
+// 判断字符是否是操作符
+bool isOp(string c) {
+    return c == "+" || c == "-" || c == "*" || c == "/";
+}
+
+string prefixToPostfix(string s) {
+    stack<string> stk;
+    string c; // 子串
+    vector<string> q;
+    stringstream s1(s);             // 构造字符串流，处理带空格的后缀表达式
+    while (s1 >> c) q.push_back(c); // 将每个子串抽取出来
+
+    for (int i = q.size() - 1; i >= 0; i--) {
+        string c = q[i];
+        if (isOp(c)) {
+            string a = stk.top();
+            stk.pop();
+            string b = stk.top();
+            stk.pop();
+            stk.push(a + " " + b + " " + c);
+        } else
+            stk.push(c); // 如果是操作数，将其转换为整数并入栈
+    }
+    return stk.top();
+}
+
+int main() {
+    string prefix = "/ + 4 2 * 3 5"; // / + 4 2 * 3 5 --> vector<>={/ + 4 2 * 3 5}
+    string postfix = prefixToPostfix(prefix);
+    cout << "前缀表达式: " << prefix << endl;
+    cout << "后缀表达式: " << postfix << endl;
+    return 0;
+}