python
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问题：
公司举办了一次TDD的研讨会，讨论的程序为实现计算器的+-*/（）。
要求采用TDD的方式进行程序的开发，并且程序是稳定的。
TDD的例子：
str0 = '1 +2 'str4 = '10+22'str5 = '10+22-33'str6 = '10+22-33*44+55 /66 'str1 = '1+(2-3)*4/5'str2 = '10+((20-3)*4)/5'str3 = '1+(((2-3)*4)/5)'strn = '100+5-2*(4*5+1)+((7/8+6)*9/5-3)'str_err = 'alsdjfk'
解决方案：
电脑的计算方式和人的大脑的计算方式类似。
1、先找到左括号和右括号，然后计算里面的值。
2、采用递归，完成所有括号的计算，并将计算得出的值替换掉括号。
3、找到*/，并按顺序进行。
4、找到+-，并按顺序进行。
知识点：
1、
return mulordev(list1) # python迭代的坑，每一次迭代必须有返回值2、
list2 = re.split(r'[+-/*/]', str6)讨论：
1、暂不考虑浮点计算。
2、计算的程序均采用递归，括号做一次，乘除做一次，加减做一次，有点冗余。
3、比较研讨会上采用C语言来实现。比较：C更加严谨，层次感强。python更加直观，通俗易懂。
源代码：
# coding:utf-8import randomimport reflag_change = 0 # 用于处理括号def new_list(str0): '''生成可计算的字符串''' # list2 = re.split(r'[+-/*/]', str6) # for m in range(0,len(list2),1): # list2[m] = list2[m].strip() # print list2 list0 = list(str0) length = len(list0) num = 0 list_new = [] for m in range(0,length,1): if '0'<=list0[m]<='9': flag_change = 1 num = 10*num +int(list0[m]) if '+'==list0[m] or '-'==list0[m] or '*'==list0[m] or '/'==list0[m] or '('==list0[m] or ')'==list0[m]: if 1 == flag_change: flag_change = 0 list_new.append(str(num)) num = 0 list_new.append(list0[m]) if length-1 == m and ')'!=list0[m]: # 不以右括号结尾 list_new.append(str(num)) return list_newdef mulordev(list1): '''计算乘除''' print list1 length = len(list1) for m in range(0,length,1): if length-1 == m: return list1 if '*' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) * int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '/' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) / int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break return mulordev(list1) # python迭代的坑，每一次迭代必须有返回值def addormin(list1): '''计算加减''' print list1 length = len(list1) for m in range(0, length, 1): if '+' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) + int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '-' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) - int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if length - 1 == m: return list1 return addormin(list1) # python迭代的坑，每一次迭代必须有返回值def brackets(list1): '''计算括号''' print list1 length = len(list1) if '(' not in list1 and ')' not in list1: return list1 flag_left = 0 flag_right = 0 for m in range(0,length,1): if '(' == list1[m]: flag_left = m if ')' == list1[m]: flag_right = m list1[flag_left] = addormin(mulordev(list1[flag_left+1 : flag_right]))[0] del list1[flag_left+1 : flag_right+1] break return brackets(list1)str0 = '1 +2 'str4 = '10+22'str5 = '10+22-33'str6 = '10+22-33*44+55 /66 'str1 = '1+(2-3)*4/5'str2 = '10+((20-3)*4)/5'str3 = '1+(((2-3)*4)/5)'strn = '100+5-2*(4*5+1)+((7/8+6)*9/5-3)'str_err = 'alsdjfk'str_cal = str_errprint '字符串为：%s \n计算结果为：%d\n' % (str_cal, int(addormin(mulordev(brackets(new_list(str_cal))))[0]))'''['100', '+', '5', '-', '2', '*', '(', '4', '*', '5', '+', '1', ')', '+', '(', '(', '7', '/', '8', '+', '6', ')', '*', '9', '/', '5', '-', '3', ')']['4', '*', '5', '+', '1']['20', '+', '1']['20', '+', '1']['21']['100', '+', '5', '-', '2', '*', '21', '+', '(', '(', '7', '/', '8', '+', '6', ')', '*', '9', '/', '5', '-', '3', ')']['7', '/', '8', '+', '6']['0', '+', '6']['0', '+', '6']['6']['100', '+', '5', '-', '2', '*', '21', '+', '(', '6', '*', '9', '/', '5', '-', '3', ')']['6', '*', '9', '/', '5', '-', '3']['54', '/', '5', '-', '3']['10', '-', '3']['10', '-', '3']['7']['100', '+', '5', '-', '2', '*', '21', '+', '7']['100', '+', '5', '-', '2', '*', '21', '+', '7']['100', '+', '5', '-', '42', '+', '7']['100', '+', '5', '-', '42', '+', '7']['105', '-', '42', '+', '7']['63', '+', '7']['70']字符串为：100+5-2*(4*5+1)+((7/8+6)*9/5-3)计算结果为：70'''******** TDD - 第一次 ****************# coding:utf-8import randomdef add(a,b): return int(a) + int(b)def min(a,b): return int(a) - int(b)def mul(a,b): return int(a) * int(b)def dev(a,b): return int(a) / int(b)str0 = '1+2'str4 = '10+22'str1 = '1+(2-3)*4/5'str2 = '10+(20-3)*4/5'str3 = '1+2-3*4/5'result = 0list0 = list(str4)print list0length = len(list0)num = 0list_new = []for m in range(0,length,1): if '0'<=list0[m]<='9': num = 10*num +int(list0[m]) if '+'==list0[m] or '-'==list0[m]: list_new.append(str(num)) list_new.append(list0[m]) num = 0 if length-1 == m: list_new.append(str(num))print list_newlength = len(list_new)for m in range(0,length,1): if '+' == list_new[m]: print m list_new[m-1] = str(int(list_new[m-1]) + int(list_new[m+1])) del list_new[m] del list_new[m] break print list_new************ TDD - 第二次 **************************str0 = '1+2'str4 = '10+22'str5 = '10+22-33'str1 = '1+(2-3)*4/5'str2 = '10+(20-3)*4/5'str3 = '1+2-3*4/5'result = 0list0 = list(str5)print list0length = len(list0)num = 0list_new = []for m in range(0,length,1): if '0'<=list0[m]<='9': num = 10*num +int(list0[m]) if '+'==list0[m] or '-'==list0[m]: list_new.append(str(num)) list_new.append(list0[m]) num = 0 if length-1 == m: list_new.append(str(num))print list_newlength = len(list_new)for m in range(0,length,1): if '+' == list_new[m]: list_new[m+1] = str(int(list_new[m-1]) + int(list_new[m+1])) if '-' == list_new[m]: list_new[m + 1] = str(int(list_new[m-1]) - int(list_new[m+1]))print list_new[-1]****************** TDD - 第三次 ********************************************str0 = '1 +2 'str4 = '10+22'str5 = '10+22-33'str6 = '10+22-33*44+55 /66 'str1 = '1+(2-3)*4/5'str2 = '10+(20-3)*4/5'str3 = '1+2-3*4/5'result = 0list2 = re.split(r'[+-/*/]', str6)for m in range(0,len(list2),1): list2[m] = list2[m].strip()print list2list0 = list(str6)print list0length = len(list0)num = 0list_new = []for m in range(0,length,1): if '0'<=list0[m]<='9': num = 10*num +int(list0[m]) if '+'==list0[m] or '-'==list0[m] or '*'==list0[m] or '/'==list0[m]: list_new.append(str(num)) list_new.append(list0[m]) num = 0 if length-1 == m: list_new.append(str(num))print list_newprint '***'def mulordev(list1): print list1 length = len(list1) for m in range(0,length,1): if length-1 == m: return list1 if '*' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) * int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '/' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) / int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break return mulordev(list1) # python迭代的坑，每一次迭代必须有返回值def addormin(list1): print list1 length = len(list1) for m in range(0, length, 1): if '+' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) + int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '-' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) - int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if length - 1 == m: return list1 return addormin(list1) # python迭代的坑，每一次迭代必须有返回值print addormin(mulordev(list_new))*************** TDD - 第四次 *******************************# coding:utf-8import randomimport redef new_list(str0): '''生成可计算的字符串''' # list2 = re.split(r'[+-/*/]', str6) # for m in range(0,len(list2),1): # list2[m] = list2[m].strip() # print list2 list0 = list(str0) length = len(list0) num = 0 list_new = [] for m in range(0,length,1): if '0'<=list0[m]<='9': num = 10*num +int(list0[m]) if '+'==list0[m] or '-'==list0[m] or '*'==list0[m] or '/'==list0[m]: list_new.append(str(num)) list_new.append(list0[m]) num = 0 if length-1 == m: list_new.append(str(num)) return list_newdef mulordev(list1): '''计算乘除''' # print list1 length = len(list1) for m in range(0,length,1): if length-1 == m: return list1 if '*' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) * int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '/' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) / int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break return mulordev(list1) # python迭代的坑，每一次迭代必须有返回值def addormin(list1): '''计算加减''' # print list1 length = len(list1) for m in range(0, length, 1): if '+' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) + int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '-' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) - int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if length - 1 == m: return list1 return addormin(list1) # python迭代的坑，每一次迭代必须有返回值str0 = '1 +2 'str4 = '10+22'str5 = '10+22-33'str6 = '10+22-33*44+55 /66 'str1 = '1+(2-3)*4/5'str2 = '10+(20-3)*4/5'str3 = '1+2-3*4/5'result = 0str_cal = str6print '字符串为：%s \n计算结果为：%d\n' % (str_cal, int(addormin(mulordev(new_list(str_cal)))[0]))****************** TDD - 第五次 *******************************************************# coding:utf-8import randomimport reflag_change = 0 # 用于处理括号def new_list(str0): '''生成可计算的字符串''' # list2 = re.split(r'[+-/*/]', str6) # for m in range(0,len(list2),1): # list2[m] = list2[m].strip() # print list2 list0 = list(str0) length = len(list0) num = 0 list_new = [] for m in range(0,length,1): if '0'<=list0[m]<='9': flag_change = 1 num = 10*num +int(list0[m]) if '+'==list0[m] or '-'==list0[m] or '*'==list0[m] or '/'==list0[m] or '('==list0[m] or ')'==list0[m]: if 1 == flag_change: flag_change = 0 list_new.append(str(num)) num = 0 list_new.append(list0[m]) if length-1 == m and ')'!=list0[m]: # 不以右括号结尾 list_new.append(str(num)) return list_newdef mulordev(list1): '''计算乘除''' print list1 length = len(list1) for m in range(0,length,1): if length-1 == m: return list1 if '*' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) * int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '/' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) / int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break return mulordev(list1) # python迭代的坑，每一次迭代必须有返回值def addormin(list1): '''计算加减''' print list1 length = len(list1) for m in range(0, length, 1): if '+' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) + int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if '-' == list1[m]: list1[m + 1] = str(int(list1[m - 1]) - int(list1[m + 1])) del list1[m - 1] del list1[m - 1] break if length - 1 == m: return list1 return addormin(list1) # python迭代的坑，每一次迭代必须有返回值def brackets(list1): '''计算括号''' print list1 length = len(list1) flag_left = 0 flag_right = 0 for m in range(0,length,1): if '(' == list1[m]: flag_left = m if ')' == list1[m]: flag_right = m list1[flag_left] = addormin(mulordev(list1[flag_left+1 : flag_right]))[0] del list1[flag_left+1 : flag_right+1] break return list1 # return brackets(list1)str0 = '1 +2 'str4 = '10+22'str5 = '10+22-33'str6 = '10+22-33*44+55 /66 'str1 = '1+(2-3)*4/5'str2 = '10+((20-3)*4)/5'str3 = '1+(((2-3)*4)/5)'str_cal = str1# print '字符串为：%s \n计算结果为：%d\n' % (str_cal, int(addormin(mulordev(new_list(str_cal)))[0]))print brackets(new_list(str_cal))print '字符串为：%s \n计算结果为：%d\n' % (str_cal, int(addormin(mulordev(brackets(new_list(str_cal))))[0]))附：研讨会版本 和 zhengrq版本**********研讨会版本*********** #include <string.h>#define OP_ADD '+'#define OP_SUB '-'#define OP_EOF '\0'typedef struct Ctx_t{ char * str; int pos;} Ctx;typedef struct Env_t{ Ctx ctx; int res;} Env;typedef struct OpEnv_t{ Ctx ctx; char op;} OpEnv;static Env num(const Ctx ctx){ Env env; env.res = ctx.str[ctx.pos] - '0'; env.ctx.str = ctx.str; env.ctx.pos = ctx.pos + 1; return env;}static OpEnv getOp(const Ctx ctx){ OpEnv env; env.op = ctx.str[ctx.pos]; env.ctx.str = ctx.str; env.ctx.pos = ctx.pos + 1; return env;}static int addOrSub(const int left, const int right, const char op){ if (op == OP_ADD) { return left + right; } else { return left - right; }}static Env calc(const Ctx ctx){ Env env; OpEnv opEnv; int res = 0; env = num(ctx); res = env.res; while ((opEnv = getOp(env.ctx)).op != OP_EOF) { env = num(opEnv.ctx); res = addOrSub(res, env.res, opEnv.op); } env.res = res; return env;}int expr(const char * str){ Ctx ctx = {(char *)str, 0}; return calc(ctx).res;}***********zhengrq版本********************expr.h:#include <stdio.h>
#include <ctype.h>
const int maxn = 1000;
int cal(const char *c, int i, int l);
int get(const char *c, int *i)
{
if (c[*i] == '(')
{
int cnt = 1, b = *i + 1;
for ((*i)++; cnt; (*i)++)
if (c[*i] == '(') cnt++;
else if (c[*i] == ')') cnt--;
return cal(c, b, *i - 1);
}
int res = 0;
for (; c[*i] && c[*i] >= '0' && c[*i] <= '9'; (*i)++) res = 10 * res + c[*i] - '0';
return res;
}
int cal(const char *c, int i, int l)
{
int s[maxn], top = 0, flag = 1;
while (i < l)
{
if (c[i] == '+') flag = 1, i++;
else if (c[i] == '-') flag = -1, i++;
else if (c[i] == '*') i++, s[top] *= get(c, &i);
else if (c[i] == '/') i++, s[top] /= get(c, &i);
else s[++top] = get(c, &i) * flag;
}
int res = 0;
while (top) res += s[top--];
return res;
}
int expr(const char *c)
{
int l = 0;
while (c[l]) l++;
return cal(c, 0, l);
}
main.cpp:
#include <stdio.h>
#include "expr.h"
#include <assert.h>
int main()
{
char c[100];
int x;
while(~scanf("%d", &x))
printf("%d\n", ~x);
while(~scanf("%s", c)) printf("%d\n", expr(c));
return 0;
}
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