h3.c

// 这个版本不支持赋值运算

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void preproccess(char *buf, int a, int b, int c, int d, int e);
void replace(char *buf, int start, int end, int number);
void mult_analytic(char *buf);
void remove_bracket(char *buf);
void analytic(char *buf, char *op);
int  calculate(char *buf, int n);

void preproccess(char *buf, int a, int b, int c, int d, int e)
{
	int i = 0;
	while(buf[i] != 0)
	{
		if(buf[i] == ' ')
			strcpy(buf+i, buf+i+1);
		else if(buf[i] == '>' && buf[i+1] == '>')
			strcpy(buf+i, buf+i+1);
		else if(buf[i] == '<' && buf[i+1] == '<')
			strcpy(buf+i, buf+i+1);
		else
		    i++;
	}
}

void replace(char *buf, int start, int end, int number)
{
	char t_buf_1[20];
	char t_buf_2[20];
	int i = 0;

	itoa(number, t_buf_1, 10);
	strcpy(t_buf_2, buf+end+1);
	strcpy(buf+start, t_buf_1);
	strcat(buf+start+strlen(t_buf_1), t_buf_2);
}

void mult_analytic(char *buf)
{
	char op[6][3] = {
		{'*', '/', '%'},
		{'+', '-', '-'},
		{'<', '>', '>'},
		{'&', '&', '&'},
		{'^', '^', '^'},
		{'|', '|', '|'}
	};
	int i = 0;

	remove_bracket(buf);
	while(i < 6)
	{
		analytic(buf, op[i++]);
	}
}

void remove_bracket(char *buf)
{
	int i = 0;
	int j = 0;
	int k = 0;
	char t_buf[20];

	while(buf[i] != 0)
	{
		if(buf[i] == '(')
			++j;
		else if(buf[i] == ')')
			++k;
		i++;
	}

	if(j != k)	// 判断括号配对
		return;
	else if(j == 0)		// 判断有无括号
		return;

	j = k = -1;
	i = 0;
	while(buf[i] != 0)	// 寻找最内层括号
	{
		if(buf[i] == '(')
			j = i;
		else if(buf[i] == ')')
		{
			k = i;
			break;
		}
		i++;
	}

	if(k != -1 && j == -1)
		return;

	// 分析括号里面的式子，存入t_buf
	strcpy(t_buf, buf + j + 1);
	t_buf[k-j-1] = '\0';

	mult_analytic(t_buf);	// 分析并计算式子

	replace(buf, j, k, atoi(t_buf));

	remove_bracket(buf);
}

void analytic(char *buf, char* op)
{
	int i = 0;
	int j = 0;
	int k = 0;

	if(buf[i] == '-' && isdigit(buf[i+1]))
		i++;
	while(buf[i] != 0)
	{
		if(buf[i] == op[0] || buf[i] == op[1] || buf[i] == op[2])
		{
			break;
		}
		i++;
	}
	if(i >= strlen(buf))
		return;

	j = k = i;
	while(isdigit(buf[j-1]))
		--j;
	if(j == 1 && buf[0] == '-' && isdigit(buf[1]))
		--j;
	if(buf[k+1] == '-' && isdigit(buf[k+2]))
		++k;
	while(isdigit(buf[k+1]))
		++k;
	replace(buf, j, k, calculate(buf + j, k-j+1));
	analytic(buf, op);
}

int calculate(char *buf, int n)
{
	char t_buf_1[20];
	char t_buf_2[20];
	char op;
	int a = 0;
	int b = 0;
	int i = 0;

	if(buf[i] == '-' && isdigit(buf[i+1]))
		i++;
	while(isdigit(buf[i]))
		i++;
	if(i >= strlen(buf))
		return atoi(buf);
	strncpy(t_buf_1, buf, i);
	t_buf_1[i] = 0;
	op = buf[i];
	strncpy(t_buf_2, buf + i + 1, n-i-1);
	t_buf_2[n-i-1] = '\0';
	a = atoi(t_buf_1);
	b = atoi(t_buf_2);
	switch(op)
	{
		case '*':	return (a*b);
		case '/':	return (a/b);
		case '%':	return (a%b);
		case '+':	return (a+b);
		case '-':	return (a-b);
		case '<':	return (a<<b);
		case '>':	return (a>>b);
		case '^':	return (a^b);
		case '&':	return (a&b);
		case '|':	return (a|b);
		default: return 0;
	}
	return 0;
}

int main(void)
{
	int a, b, c, d, e;
	char buf[60];

	puts("input a b c d e");
	scanf("%d %d %d %d %d", &a, &b, &c, &d, &e);
	fflush(stdin);
	puts("input a expression");
	gets(buf);

	preproccess(buf, a, b, c, d, e);
	mult_analytic(buf);

	printf("= %d\n", atoi(buf));

	system("pause");
	return 0;
}