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expression_evaluation2.cpp
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expression_evaluation2.cpp
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#include <stack>
#include <math.h>
#include <stdio.h>
#include <cstdlib>
#include <stdlib.h>
#include <string.h>
#include <iostream>
using namespace std;
int isNum(char c){
return (c>='0'&&c<='9');
}
int convert(char z){
int v = 9999;
switch (z){
//一级运算符
case '+': v = 1; break;
case '-': v = 1; break;
//二级运算符
case '*': v = 2; break;
case '/': v = 2; break;
case '%': v = 2; break;
//三级运算符
case '^': v = 4; break;
//一般弱
case '(': v = -1000; break;
//一般强
case ')': v = 1000; break;
//前弱后强
case '#': v = 500; break;
}
return v;
}
int judge(char a, char b){
int q = convert(a);if(q==500)q-=1000;
int p = convert(b);
int flag1 = q - p;
int flag2 = q + p;
int flag3 = abs(q) + abs(p);
if (flag3 < 10){
//仅有基本运算符
if (flag1 < 0 || flag3 == 8) return -1;
//a^b^c要转为abc^^
else return 1;
}else if (abs(abs(flag3) - 1000) < 10 || abs(abs(flag3) - 2000) < 10){
//括号与基本操作符
if (flag2 < 0) return -1;
else if (flag2 > 0) return 1;
else if (flag2 == 0 && flag1 != 2000) return 0;
else return -2;
}else if (flag3 == 1500 && flag1 == 500){
//# vs ><
if (flag2 < 0) return -1;
else return 1;
}else if (abs(abs(flag3) - 500) < 10){
//#与基本操作符
if (abs(flag1) < 500) return 1;
if (abs(flag1) > 500) return -1;
}else {
return -2;
}
return -2;
}
int flag = 0;
int operate(int a, char op, int b){
int res = 0;
switch(op){
case '+':{ res = a + b; break;}
case '-':{ res = a - b; break;}
case '*':{ res = a * b; break;}
case '/':{
if(b == 0){
flag = -1;
break;
}
res = a / b;
break;
}
case '%':{
if(b == 0){
flag = -1;
break;
}
res = a % b;
break;
}
case '^':{
if(b < 0) flag = -2;
res = pow(a, b);
break;
}
default:{
flag = -3;
break;
}
}
return res;
}
int main(){
int times;
if(scanf("%d", ×)!=1)exit(0);
while(times--){
flag = 0;
stack<int> opnd;
stack<char> optr;
optr.push('#');
int i = 1;
int a, b, res;
char op;
int minus = 1;
char exp[200];
memset(exp, '0', sizeof(exp));
if(scanf("%s", exp+1)!=1)exit(0);
exp[0] = '#';
exp[strlen(exp)] = '#';
while(exp[i] != '#' || optr.top() != '#'){
if(isNum(exp[i])){
int num = exp[i] - '0';
int ti = 1;
while(isNum(exp[i+ti])){
num = num * 10 + (exp[i+(ti++)] - '0');
}
num *= minus;
minus = 1;
opnd.push(num);
i += ti;
}else if(exp[i] == '-' && isNum(exp[i+1]) && (!isNum(exp[i-1]) || !exp[i-1] == ')')){
minus = -1;
i++;
}else if(exp[i] == '(' && !(isNum(exp[i+1]) || exp[i+1] == '-' || exp[i+1] == '#' || exp[i+1] == '(')){
flag = -6;
}else{
switch(judge(optr.top(), exp[i])){
case -1:{
optr.push(exp[i++]);
break;
}case 0:{
optr.pop();
i++;
break;
}case 1:{
if(!opnd.empty()) {a = opnd.top(); opnd.pop();}
else {flag = -5; break;}
if(!opnd.empty()) {b = opnd.top(); opnd.pop();}
else {flag = -5; break;}
op = optr.top();
optr.pop();
res = operate(b, op, a);
if (flag < 0) break;
opnd.push(res);
break;
}case -2:{
flag = -4;
break;
}
}
}
if(flag < 0) break;
}//字符循环
if(flag < 0 || optr.size() != 1 || opnd.size() != 1){
if(flag == -1) printf("Divide 0.\n");
else printf("error.\n");
}else if (flag == 0){
printf("%d\n", opnd.top());
}//else if (flag == -1)
}//次数循环
}