问给定一个用数学符号分隔整数的列表，找出某个值是否可以通过放置大括号来计算。

EN

from itertools import permutations

formula = [6,'-',4,'*',2,'+',3] ;
searchedValue = 10 ;

# operators are on odd positions . 
operatorsPositions = list(range(1,len(formula),2)) # [1, 3, 5]
# prepare all permutations eq all parenthesis order . return an array of tuple
permut = list(permutations(operatorsPositions))
print("**** {0} permutations to be tested ****".format(len(permut)))
print(permut)


# around an operator , two operands . return result
def calcAround(aFormula,position):
 op1 = aFormula[position -1]
 op2 = aFormula[position +1]
 operator = aFormula[position]
 # optional trace operation
 # print("calculate ({0:2d} {1} {2:2d})".format(op1,operator,op2));
 if (operator == "-"): return op1-op2;
 if (operator == "+"): return op1+op2;
 if (operator == "*"): return op1*op2;
 if (operator == "/"): return op1/op2;
 #--------------------

# 'op1', 'operator', 'op2'  replaced by result in formula
def reduceAtPosition(someformula,position):
    result = calcAround(someformula,position);
    formulaNew =[];
    for i in range (0,position-1): formulaNew.append(someformula[i]);
    formulaNew.append(result);
    for i in range (position+2,len(someformula)):formulaNew.append(someformula[i]);
    return formulaNew;

# ------- main part --------
#  set to store unique possible results 
allResults = set(())
# try each permutation of operators order 
for aTest in permut: 
  aPermut = list(aTest) # better to have an array in place of tuple
  print('----------------')
  # make a new copy each tour 
  lTempo = formula.copy()
  print("operators sequence: {0}".format(aPermut))

  while(len(aPermut)>0):
    print(lTempo)
    anOpIndice = aPermut[0]
    lTempo = reduceAtPosition(lTempo,anOpIndice);
    # remove first done 
    aPermut = aPermut[1:]  
    for i in range(0,len(aPermut)):
      if (aPermut[i]>anOpIndice): aPermut[i] -= 2
  # 
  final = lTempo[0]
  print("result: {0}".format(final))
  # to respond to question 
  if(final == searchedValue): 
    print('*** found {0} with order or operators positions: {1} '.format(final,aTest))
  
  allResults.add(final)
print('---- all possible results : {0}'.format(allResults))

**** 6 permutations to be tested ****
[(1, 3, 5), (1, 5, 3), (3, 1, 5), (3, 5, 1), (5, 1, 3), (5, 3, 1)]
----------------
operators sequence: [1, 3, 5]
[6, '-', 4, '*', 2, '+', 3]
[2, '*', 2, '+', 3]
[4, '+', 3]
result: 7
----------------
operators sequence: [1, 5, 3]
[6, '-', 4, '*', 2, '+', 3]
[2, '*', 2, '+', 3]
[2, '*', 5]
result: 10
*** found 10 with order or operators positions: (1, 5, 3) 
----------------
operators sequence: [3, 1, 5]
[6, '-', 4, '*', 2, '+', 3]
[6, '-', 8, '+', 3]
[-2, '+', 3]
result: 1
----------------
operators sequence: [3, 5, 1]
[6, '-', 4, '*', 2, '+', 3]
[6, '-', 8, '+', 3]
[6, '-', 11]
result: -5
----------------
operators sequence: [5, 1, 3]
[6, '-', 4, '*', 2, '+', 3]
[6, '-', 4, '*', 5]
[2, '*', 5]
result: 10
*** found 10 with order or operators positions: (5, 1, 3) 
----------------
operators sequence: [5, 3, 1]
[6, '-', 4, '*', 2, '+', 3]
[6, '-', 4, '*', 5]
[6, '-', 20]
result: -14
---- all possible results : {1, 7, 10, -14, -5}