学习笔记47-找出n个数中第k大的数

def findNum(a,first,last,dest):
if first>=last:
return a[dest]
i=first
j=last
key=a[i]
while i<j:
while i<j and a[j]>=key:
j-=1
a[i]=a[j]
while i<j and a[i]<=key:
i+=1
a[j]=a[i]
a[i]=key
if i==dest:
return a[i]
elif i<dest:
return findNum(a,i+1,last,dest)
else:
return findNum(a,first,i-1,dest)

def permutation(a,m,n):
if m==n:
print findNum(a,0,len(a)-1,len(a)//2)
else:
for i in range(m,n):
a[m],a[i]=a[i],a[m]
permutation(a,m+1,n)
a[m],a[i]=a[i],a[m]

a=[0,1,2,3,4]
permutation(a,0,len(a))