有错误，，算法导论，无哨兵 情况
```
import sys
class mergesort():
def merge_sort(self, A, p, r):
if p < r:
q = (p + r) / 2
self.merge_sort(A, p, q)
self.merge_sort(A, q+1, r)
self.merge(A, p, q, r)
return A
def merge(self, A, p, q, r):
n1 = q - p + 1
n2 = r - q
L = [0 for i in range(n1+1)]
R = [0 for i in range(n2+1)]
for i in range(n1):
L[i] = A[p+i]
for j in range(n2):
R[j] = A[q+j+1]
L[n1] = sys.maxint
R[n2] = sys.maxint
i = 0; j = 0
for k in range(p, r):
if (i!=n1 and j!=n2):
if L[i] <= R[j]:
A[k] = L[i]
i += 1
else:
A[k] = R[j]
j += 1
else:
onlyonetime1=1
onlyonetime2=1
if ( i==n1 and onlyonetime1) :
#A[k] = R[j]
#j += 1
kaka=0
for nn in range(j,n2):
A[k+kaka]=R[nn]
kaka+=1
onlyonetime1=0
if (j==n2 and onlyonetime2):
#j==n2
#A[k] = R[j]
#j += 1
baba=0
for mm in range(i,n1):
A[k+baba]=L[mm]
baba+=1
onlyonetime2=0
sort = mergesort()
A = [1,3,5,7,9,11,20,40,60,80,100,120]
print sort.merge_sort(A, 0, len(A)-1)
```
123123
```
$python main.py
Traceback (most recent call last): File "main.py", line 67, in print sort.merge_sort(A, 0, len(A)-1) File "main.py", line 9, in merge_sort self.merge_sort(A, q+1, r) File "main.py", line 10, in merge_sort self.merge(A, p, q, r) File "main.py", line 50, in merge A[k+kaka]=R[nn]IndexError: list assignment index out of range
```
原因未找到，先记录下来
