'commit'

TangDou/LanQiaoBei/LanQiao14GuoSai/3.cpp

@@ -0,0 +1,61 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+stack<int> stk;
+stack<char> op;
+
+unordered_map<char, int> g{{'+', 1}, {'-', 1}, {'*', 2}, {'/', 2}};
+
+
+void eval() {
+    int a = stk.top();
+    stk.pop();
+
+    int b = stk.top();
+    stk.pop();
+
+    char p = op.top();
+    op.pop();
+
+    int r;
+
+    if (p == '+') r = b + a;
+    if (p == '-') r = b - a;
+    if (p == '*') r = b * a;
+    if (p == '/') r = b / a;
+
+    stk.push(r);
+}
+
+int main() {
+    string s;
+    getline(cin, s);
+
+    for (int i = 0; i < s.size(); i++) {
+        if (s[i] == ' ') continue; // 过滤掉空格
+        if (isdigit(s[i])) {
+            int x = 0;
+            while (i < s.size() && s[i] >= '0' && s[i] <= '9') {
+                x = x * 10 + s[i] - '0';
+                i++;
+            }
+            i--;
+
+            stk.push(x);
+        }
+
+        else if (s[i] == '(')
+            op.push(s[i]);
+        else if (s[i] == ')') {
+            while (op.top() != '(') eval();
+            op.pop();
+        } else {
+            while (op.size() && g[op.top()] >= g[s[i]]) eval();
+            op.push(s[i]);
+        }
+    }
+    while (op.size()) eval();
+
+    printf("%d\n", stk.top());
+    return 0;
+}