python 寻找没有出现的数字

Missing numberGiven an array containing all numbers from 1 to N with the exception of one print the missing number to the standard output.Example input:array: 5 4 1 2Example output:3////////////////////////////打算使用二进制的特性，但编译器的精度不给过。。

import mathdef find_missing_number(v):# Write your code here# To print results to the standard output you can use print# Example: print "Hello world!"maxNum=0sumNum = 2for item in v:sumNum+=2**itemif(item > maxNum):maxNum =itemprint math.floor( math.log(2**(maxNum+1) - sumNum - 2, 2) )

////////////////////////////那就用等差数列公式吧

import mathdef find_missing_number(v):# Write your code here# To print results to the standard output you can use print# Example: print "Hello world!"maxNum=NoneminNum =()sumNum = 0for item in v:sumNum+=itemif(item > maxNum):maxNum =itemif (item < minNum):minNum = itemif minNum != 1:print '1'else:print (minNum+maxNum)*(len(v)+1)/2  - sumNum

///////////////////////////////////////另外有更简洁的

def find_missing_number(v):n = len(v) + 1print(n * (n+1) / 2 - sum(v))