Parse math expression with c

Math Expression Parser.c

/**
*Math Expression Parser
*
*Author: Fing
*
*First Created: 2015.12.13
*
*/

#include "stdio.h"
/*Try with minimal libarary usage*/

int powr(int x, int n);   //计算x^n
int isNum(char ch);  //判断一个字符是否是数字
int isOp(char ch);  //判断是否为运算符
int isPar(char ch);  //判断是否为括号
int cmpPrio(char a, char b);  // 比较运算符的优先级 a>b?
int ch2num(char ch);  //将字符转换为数字
int getNum(char input[], int i); //取多位数字
void pushNum(int numb[], int top, int number);  //向数字栈中添加数字
int popNum(int numb[], int top);  //数字栈中弹出数字
void pushOp(char op[], int top, char operat);  //向运算符栈中添加运算符
char popOp(char op[], int top);  //运算符栈中弹出运算符
int calc(int a, int b, char c); //计算两个数字

int Calculate(char input[], int length);  //计算结果

char op[50] = { '\0' };    //存放运算符
int num[50] = { '\0' };   //存放数字
int op_top = -1;
int num_top = -1;

int leftBracketCount = 0;  //左括号计数
int rightBracketCount = 0;  //有括号计数
int opCount = 0; //运算符计数
int numCount = 0;  //数字计数

int main()
{
	char input[50];
	int length = 1;
	input[0] = getchar();
	int i;
	for (i = 1; i <= 50; i++)
	{
		input[i] = getchar();
		length++;
		if (input[i] == 10) break;
	}
	length--;
	printf("= %d\n", Calculate(input, length));
	getchar(); getchar();

}

//幂运算
int powr(int x, int n)
{
	int i;
	int result = 1;
	for (i = 1; i <= n; i++)
		result *= x;
	return result;
}

//判断是否是数字
int isNum(char ch)
{
	if (ch >= '0' && ch <= '9') return 1;
	else return 0;
}

//判断是否是运算符
int isOp(char ch)
{
	if (ch >= '+' || ch == '-' || ch == '*' || ch == '/') return 1;
	else return 0;
}

//判断是否是括号
int isPar(char ch)
{
	if (ch == '(' || ch == ')') return 1;
	else return 0;
}

//比较运算符的优先级
int cmpPrio(char a, char b)
{
	if (a == '*' || a == '/') return 1;
	else return 0;
}

//字符->数字
int ch2num(char ch)
{
	return (ch - '0');
}

//转化多位数字
int getNum(char input[], int i)
{
	int j, count;
	count = 1;
	int result = 0;
	for (j = i + 1; j<50; j++)
	{
		if (isNum(input[j])) count++;
		else break;
	}
	for (j = i; j < i + count; j++)
	{
		result = result + ch2num(input[j])*powr(10, count - (j - i + 1));
	}
	return result;
}

//压入数字
void pushNum(int num[], int top, int number)
{
	num[top + 1] = number;
	num_top++;
}

//弹出数字
int popNum(int numb[], int top)
{
	int t;
	t = numb[top];
	numb[top] = '\0';
	num_top--;
	return t;
}

//压入运算符
void pushOp(char op[], int top, char operat)
{
	op[top + 1] = operat;
	op_top++;
}

//弹出运算符
char popOp(char op[], int top)  //运算符栈中弹出运算符
{
	char t;
	t = op[top];
	op[top] = '\0';
	op_top--;
	return t;
}

//计算两个数字
int calc(int a, int b, char c)
{
	switch (c)
	{
	case '+': return a + b; break;
	case '-': return a - b; break;
	case '*': return a*b; break;
	case '/': return a / b; break;
	default: break;
	}
}



//计算
int Calculate(char input[], int length)
{
	int i;
	//遍历
	for (i = 0; i<length; i++)
	{
		if (isNum(input[i]))  //如果是数字，读取数字，入栈
		{
			int j;
			pushNum(num, num_top, getNum(input, i));
			for (j = i; j<length; j++)
			{
				if (!isNum(input[j]))  //不是数字，改变循环起点
				{
					i = j - 1;
					break;
				}
			}
			numCount++;   //数字计数++
		}
		else if (isOp(input[i]))  //如果是运算符，判断优先级，计算栈顶两个数字
		{
			if (op_top>0)  //如果有运算符，与上一个运算符比较
			{
				if (!isPar(op[op_top]))  //如果上一个不是括号，则比较
				{
					if (cmpPrio((input[i]), op[op_top]))  //优先级高的话，入栈
					{
						pushOp(op, op_top, input[i]);
					}
					else                        //否则计算栈顶两个数字，再将input入栈
					{
						int a, b;
						b = popNum(num, num_top);
						a = popNum(num, num_top);
						pushNum(num, num_top, calc(a, b, popOp(op, op_top)));
						pushOp(op, op_top, input[i]);
					}
				}
				else  //如果上一个是括号的话，
				{
					if (input[i] == '-' && input[i - 1] == '(')  //负数的判断
					{
						pushNum(num, num_top, 0);  //在栈顶插入0
						pushOp(op, op_top, input[i]);  //在栈顶压入减号
					}
					else
					{
						pushOp(op, op_top, input[i]);
					}
				}
			}
			else   //如果前一个没有运算符了
			{
				pushOp(op, op_top, input[i]);
			}

		}
		else if (isPar(input[i]))   //如果是括号的话
		{
			if (input[i] == '(')  //如果是左括号，直接进栈
			{
				pushOp(op, op_top, input[i]);
				//leftBracketCount++;
			}
			else  //右括号的情况
			{
				int j = op_top;
				while (op[j] != '(')  //遍历，计算
				{
					int a, b;
					b = popNum(num, num_top);
					a = popNum(num, num_top);
					pushNum(num, num_top, calc(a, b, popOp(op, op_top)));
					j--;
				}
				char c;
				c = popOp(op, op_top);   //弹出左边括号
				//leftBracketCount--;
			}
		}
		//int m;
		//for (m = 0; m <= op_top; m++)
		//	printf("%c ", op[m]);
		////printf(" %d",op_top);
		//printf("\n");
		//for (m = 0; m <= num_top; m++)
		//	printf("%d ", num[m]);
		////printf(" %d", num_top);
		//printf("\n");
	}
	int k;
	for (k = op_top; k >= 0; k--)
	{
		int a, b;
		b = popNum(num, num_top);
		a = popNum(num, num_top);
		pushNum(num, num_top, calc(a, b, popOp(op, op_top)));
	}
	return num[0];
}