Hm3

Exercise/Homework3/表达式树模板.cpp

@@ -0,0 +1,146 @@
+#include <bits/stdc++.h>
+using namespace std;
+
+struct Node {
+    char sign;       // <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ҷ<EFBFBD>ӽڵ<D3BD>Ϊ '?'
+    long long num;   // <20><><EFBFBD><EFBFBD>
+    Node* left;
+    Node* right;
+    
+    Node(): sign('?'), num(-1), left(nullptr), right(nullptr) {}
+    Node(char s): sign(s), num(-1), left(nullptr), right(nullptr) {}
+    Node(long long n): sign('?'), num(n), left(nullptr), right(nullptr) {}
+};
+
+// <20><><EFBFBD><EFBFBD><EFBFBD>ݣ<EFBFBD><DDA3><EFBFBD><EFBFBD><EFBFBD>
+long long fastpow(long long base, long long exp){
+    long long res = 1;
+    while(exp > 0){
+        if(exp & 1) res *= base;
+        base *= base;
+        exp >>= 1;
+    }
+    return res;
+}
+
+// <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȼ<EFBFBD>
+int level(char c){
+    switch(c){
+        case '+': case '-': return 1;
+        case '*': case '/': return 2;
+        case '^': return 3;
+        default: return 0;
+    }
+}
+
+// <20>ҵ<EFBFBD><D2B5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ȼ<EFBFBD><C8BC><EFBFBD><EFBFBD>͵<EFBFBD><CDB5><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
+int findexp(const string &s, int l, int r){
+    int pos = -1;
+    int minLevel = 114514;
+    int balance = 0; // <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>
+    for(int i = r; i >= l; --i){ // <20>ҽ<EFBFBD><D2BD>ϣ<EFBFBD><CFA3><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>ұ<EFBFBD>
+        if(s[i] == ')') balance++;
+        else if(s[i] == '(') balance--;
+        else if(balance == 0 && level(s[i]) > 0){
+            if(level(s[i]) <= minLevel){
+                minLevel = level(s[i]);
+                pos = i;
+            }
+        }
+    }
+    return pos;
+}
+
+// <20>ַ<EFBFBD><D6B7><EFBFBD>ת<EFBFBD><D7AA><EFBFBD><EFBFBD>
+long long toNum(const string &s, int l, int r){
+    long long tmp = 0;
+    while(l <= r && isspace((unsigned char)s[l])) l++;
+    while(r >= l && isspace((unsigned char)s[r])) r--;
+    if(l > r) return 0;
+    for(int i = l; i <= r; ++i){
+        if(!isdigit(s[i])) return 0;
+        tmp = tmp * 10 + (s[i] - '0');
+    }
+    return tmp;
+}
+
+class Expression {
+public:
+    string exp;
+    Node* root;
+    long long result;
+    bool isValid;
+    
+    Expression(const string &s): exp(s), root(nullptr), result(0), isValid(true) {}
+
+    Node* build(const string &s, int l, int r){
+        while(l <= r && s[l] == ' ') l++;
+        while(l <= r && s[r] == ' ') r--;
+        if(l > r) return nullptr;
+
+        // <20><><EFBFBD><EFBFBD><EFBFBD><EFBFBD><EFBFBD>Ŵ<EFBFBD><C5B4><EFBFBD>
+        if(s[l] == '(' && s[r] == ')'){
+            int balance = 0;
+            bool hasOuter = true;
+            for(int i = l; i <= r; ++i){
+                if(s[i] == '(') balance++;
+                else if(s[i] == ')') balance--;
+                if(balance == 0 && i < r){
+                    hasOuter = false;
+                    break;
+                }
+            }
+            if(hasOuter) return build(s, l+1, r-1);
+        }
+
+        int pos = findexp(s, l, r);
+        if(pos == -1){
+            long long val = toNum(s, l, r);
+            return new Node(val);
+        }
+
+        Node* tmp = new Node(s[pos]);
+        tmp->left = build(s, l, pos-1);
+        tmp->right = build(s, pos+1, r);
+        return tmp;
+    }
+
+    long long calc(Node* r, bool &v){
+        if(!r) return 0;
+        if(r->sign == '?') return r->num;
+
+        long long left = calc(r->left, v);
+        long long right = calc(r->right, v);
+
+        switch(r->sign){
+            case '+': return left + right;
+            case '-': return left - right;
+            case '*': return left * right;
+            case '/':
+                if(right == 0){ v = false; return 0; }
+                return left / right;
+            case '^':
+                if(right < 0){ v = false; return 0; }
+                return fastpow(left, right);
+            default: return 0;
+        }
+    }
+
+    void calc(){
+        isValid = true;
+        result = calc(root, isValid);
+    }
+};
+
+int main(){
+    string s;
+    while(getline(cin, s)){
+        Expression tree(s);
+        tree.root = tree.build(s, 0, s.length()-1);
+        tree.calc();
+        if(tree.isValid) cout << tree.result << endl;
+        else cout << "INVALID" << endl;
+    }
+    return 0;
+}
+