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vector<int> nums;
vector<char> ops;
int grade(char op) { switch (op) { case '(': return 1; case '+': case '-': return 2; case '\*': case '/': return 3; } return 0; }
void calc(char op) {
int y = *nums.rbegin(); nums.pop_back(); int x = *nums.rbegin(); nums.pop_back(); int z; switch (op) { case '+': z = x + y; break; case '-': z = x - y; break; case '_': z = x _ y; break; case '/': z = x / y; break; }
nums.push_back(z); }
int solve(string s) { nums.clear(); ops.clear(); int top = 0, val = 0; for (int i = 0; i < s.size(); i++) {
if (s[i] >= '0' && s[i] <= '9') { val = val * 10 + s[i] - '0'; if (s[i+1] >= '0' && s[i+1] <= '9') continue;
nums.push_back(val); val = 0; }
else if (s[i] == '(') ops.push_back(s[i]);
else if (s[i] == ')') { while (*ops.rbegin() != '(') {
calc(*ops.rbegin()); ops.pop_back(); } ops.pop_back(); }
else { while (ops.size() && grade(*ops.rbegin()) >= grade(s[i])) { calc(*ops.rbegin()); ops.pop_back(); } ops.push_back(s[i]); } } while (ops.size()) { calc(*ops.rbegin()); ops.pop_back(); }
return \*nums.begin(); }
JAVA
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