The abuse of greatness is when it disjoins remorse from power.
#include #include #include #include #include #include #include using namespace std; //栈内优先级 map isp; //入栈优先级 map icp; //分离表达式 list Tokenize(const string& str,const string& delimiters){ list tokens; string::size_type delimPos = 0, tokenPos = 0, pos = 0; if(str.length()<1) return tokens; while(1){ delimPos = str.find_first_of(delimiters, pos); tokenPos = str.find_first_not_of(delimiters, pos); if(string::npos != delimPos){ if(string::npos != tokenPos){ if(tokenPos tokens.push_back(str.substr(pos,delimPos-pos)); }else{ tokens.push_back(""); } }else{ tokens.push_back(""); } pos = delimPos+1; } else { if(string::npos != tokenPos){ tokens.push_back(str.substr(pos)); } else { tokens.push_back(""); } break; } } return tokens; } inline bool isNumber(char c){ return c=='.'||'0'<=c&&c<='9'; } inline bool isSymbol(string op) { return op=="+"||op=="-"||op=="*"||op=="/"||op=="%"||op=="^"||op=="("||op==")"; } inline bool isSpace(char c){ return c==' '||c=='\t'||c=='\n'||c=='\r'; } //格式化&分离表达式 list toExpressionArray(string exp){ string fexp; const char* data = exp.data(); int idx = 0; int len = exp.length(); for(;idx char c = data[idx]; if(isNumber(c)){ fexp.push_back(c); } else if(!isSpace(c)){ fexp.push_back(' '); fexp.push_back(c); fexp.push_back(' '); } } return Tokenize(fexp," "); } //中序换前序 list m2l(list m) { list l; stack s; string op; string y; s.push("#"); for(list::const_iterator i = m.begin();i!=m.end();i++){ op = *i; if(op=="") continue; if(!isSymbol(op)){ l.push_back(op); }else{ if(icp[op]>isp[s.top()]){ s.push(op); }else if(op==")"){ y = s.top(); s.pop(); while(y!="("){ l.push_back(y); y = s.top(); s.pop(); } }else{ y = s.top(); s.pop(); while(icp[op] l.push_back(y); y = s.top(); s.pop(); } s.push(y); s.push(op); }//if2 }//if1 }//for while(s.top()!="#"){ l.push_back(s.top()); s.pop(); } return l; } //计算 double _calc(double o1, double o2, char op) { switch(op){ case '+':{ return o1+o2; } case '-':{ return o1-o2; } case '*':{ return o1*o2; } case '/':{ return o1/o2; } case '^':{ return pow(o1,o2); } } return 0; } //计算前序表达式 double calc(list in){ stack sk; for(list::const_iterator i = in.begin();i!=in.end();i++){ string op = *i; if(!isSymbol(op)){ sk.push(atof(op.data())); }else{ double o2 = sk.top(); sk.pop(); double o1 = sk.top(); sk.pop(); char o = op.data()[0]; double r = _calc(o1,o2,o); sk.push(r); } } return sk.top(); } //没用 void printList(list l){ int x=0; for(list::const_iterator i = l.begin();i!=l.end();i++){ cout<<++x<<":"<<*i< } } int main() { isp["+"]=3; isp["-"]=3; isp["*"]=5; isp["/"]=5; isp["%"]=5; isp["^"]=5; isp["("]=1; isp[")"]=6; isp["#"]=0; icp["+"]=2; icp["-"]=2; icp["*"]=4; icp["/"]=4; icp["%"]=4; icp["^"]=4; icp["("]=6; icp[")"]=1; icp["#"]=0; string exp; cout<<"Exp:"; cin>>exp; list l1 = toExpressionArray(exp); printList(l1); list l2 = m2l(l1); printList(l2); double r = calc(l2); cout<<"Result:"< return 0; }
c ++编程示例在自由空间中移动3D盒子
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c ++编程示例
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