计算表达式值

来源：互联网发布：知乎杭州电子科技大学编辑：程序博客网时间：2024/06/05 16:48
#include <stdio.h>#include <math.h>#include <string.h>#include <algorithm>#include <iostream>#include <string>#include <vector>#include <queue>#include <stack>#include <set>#include <map>using namespace std;const int N = 1e3 + 10;stack<int> op, br;stack<double> num;char str[N];void initStack() {  while (!op.empty()) op.pop();  while (!br.empty()) br.pop();  while (!num.empty()) num.pop();}int getType(char c) {  if (c >= '0' && c <= '9')    return 0;  else if (c == '+' || c == '-')    return 1;  else if (c == '*' || c == '/')    return 1;  else if (c == '(' || c == ')')    return 2;  else if (c == '[' || c == ']')     return 2;  else if (c == '{' || c == '}')    return 2;  else    return -1;}int transOp(char c) {  if (c == '+')    return 0;  else if (c == '-')    return 1;  else if (c == '*')    return 2;  else if (c == '/')    return 3;  return -1;}int transBr(char c) {  if (c == '(')    return 0;  else if (c == ')')    return 1;  else if (c == '[')    return 2;  else if (c == ']')    return 3;  else if (c == '{')    return 4;  else if (c == '}')    return 5;  else    return -1;}bool cal(int fp) {  double num2, num1;  if (!num.empty()) { // get second number    num2 = num.top();    num.pop();  }  else {    printf("Wrong position of operator\n");    return false;  }  if (!num.empty()) { // get first number    num1 = num.top();    num.pop();  }  else {                printf("Wrong position of operator\n");    return false;  }  double ans = 0;  if (fp % 4 == 0) {    ans = num1 + num2;  }  else if (fp % 4 == 1) {    ans = num1 - num2;  }  else if (fp % 4 == 2) {    ans = num1 * num2;  }  else if (fp % 4 == 3) {    if (num2 == 0) {      printf("Divide zero\n");      return false;    }    ans = num1 / num2;  }  num.push(ans);  return true;}bool solve(double &res) {  initStack();  int len = strlen(str);  int plus = 0; // operator addition  for (int i = 0; i < len; i++) {    int type = getType(str[i]);    if (type == 0) { // number      double sum = str[i++] - '0';      double pl = 10;      while (i < len && (type = getType(str[i])) == 0) { // before decimal        sum = sum * pl + str[i] - '0';        i++;      }      if (i < len && str[i] == '.') { // decimal        pl = 0.1;        i++;        while (i < len && (type = getType(str[i])) == 0) { // after decimal          sum = sum + (str[i] - '0') * pl;          i++;          pl *= 0.1;        }      }      else if (i < len && type == -1) { // illegal character        printf("Illegal character: %c\n", str[i]);        return false;      }      num.push(sum);      i--;    }    else if (type == 1) { // operator      int p = transOp(str[i]) + plus;      while (!op.empty()) {        int fp = op.top();        if (fp >= p) { // now operator is lower          op.pop();          if (!cal(fp))            return false;        }        else { // now operator is higher          break;        }      }      op.push(p);    }    else if (type == 2) { // bracket      int t = transBr(str[i]);      if (t % 2) { // right bracket        if (br.empty()) {          printf("Brackets are not mactch\n");          return false;        }        else {          int ft = br.top();          br.pop();          if (t - 1 != ft) {            printf("Brackets are not mactch\n");            return false;          }        }        plus -= 4;      }      else { // left bracket        plus += 4;        br.push(t);      }    }    else { // illegal character      printf("Illegal character: %c\n", str[i]);      return false;    }  }  if (!br.empty()) { // check bracket    printf("Brackets are not mactch\n");    return false;  }  while (!op.empty()) { // calculate rest    int fp = op.top();    op.pop();    if (!cal(fp))      return false;  }  if (num.empty()) { // no number left    printf("No Number\n");    return false;  }  else if (num.size() > 1) { // too many numbers    printf("Too many numbers\n");    return false;  }  res = num.top();  return true;}int main() {  scanf("%s", str);  double res = -1;  if (solve(res))    printf("%.3lf\n", res);  return 0;}
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