算法导论--不用哨兵实现归并排序

题目：
重写MERGE过程，使其不使用标记，而是在数组L或R将其所有元素复制回A然后将另一个数组的其余部分复制回A时停止。

伪代码

MERGE(A, p, q, r)
n1 = q - p + 1
n2 = r - q
let L[1..n₁] and R[1..n₂] be new arrays
for i = 1 to n₁
L[i] = A[p + i - 1]
for j = 1 to n₂
R[j] = A[q + j]
i = 1
j = 1
for k = p to r
if i > n₁
A[k] = R[j]
j = j + 1
else if j > n₂
A[k] = L[i]
i = i + 1
else if L[i] ≤ R[j]
A[k] = L[i]
i = i + 1
else
A[k] = R[j]
j = j + 1

代码

#include  <stdio.h>

void merge（int A []，int p，int q，int r）{
int i，j，k;

int n1 = q  -  p + 1 ;
int n2 = r  -  q;

int L [n1];
int R [n2];

for（i = 0 ; i <n1; i ++）
L [i] = A [p + i];
for（j = 0 ; j <n2; j ++）
R [j] = A [q + j + 1 ];

for（i = 0，j = 0，k = p; k <= r; k ++）{
if（i == n1）{
A [k] = R [j ++];
} else  if（j == n2）{
A [k] = L [i ++];
} else  if（L [i] <= R [j]）{
A [k] = L [i ++];
} else {
A [k] = R [j ++];
}
}
}

void merge_sort（int A []，int p，int r）{
if（p <r）{
int q =（p + r）/ 2 ;
merge_sort（A，p，q）;
merge_sort（A，q + 1，r）;
合并（A，p，q，r）;
}
}