C語言實現靜態鏈表的方法

在動手之前我一直以為靜態鏈表和動態鏈表沒有什麼差別，細細一想才發現，原來靜態鏈表之中隱藏著一個非常值得討論的話題——記憶體管理。

靜態鏈表的“靜態”二字是指記憶體的來源為靜態記憶體（通常用全域數組）。與動態鏈表不同，在靜態鏈表中節點記憶體的申請與釋放都需要自我維護，由於這裡是鏈表，也很容易想到將空餘的節點連結起來形成一個free_list，每次需要時從free_list頭部取出一個節點，釋放時再將節點加到頭部，這樣就能夠非常容易的實現鏈表的其他動作。

複製代碼 代碼如下:// 靜態鏈表 的實現
#include <stdio.h>

#define MAXN 16 // capacity of list.
typedef int element; // element type.

// define boolean type:
typedef int bool;
#define true -1
#define false 0

#define NPTR -1 // null pointer definition. can not between 0 to MAXN-1.
typedef int pointer;

#define DEBUGVAL(x) printf("%s: %d\n", #x, (x)); // a macro for debug.

struct __node
{
element data;
pointer next;
}SLList[MAXN];
pointer ifree, idata;

#define nextof(p) SLList[p].next
#define dataof(p) SLList[p].data

#define _alloc(d) ifree; dataof(ifree)=(d); ifree != NPTR ? ifree=nextof(ifree) : NPTR
#define _free(p) nextof(p)=ifree; ifree = p

void init()
{
int i;
ifree = 0;
idata = NPTR;
for( i=0; i < MAXN-1; i++)
nextof(i) = i+1;
nextof(i) = NPTR;
}

// clear all nodes.
void clear() { init(); }

// push val to front.
bool push_front(element val)
{
pointer tmp, np;
if( ifree != NPTR ) {
np = _alloc(val);
nextof(np) = idata;
idata = np;
return true;
}
return false;
}

// push val to end of list.
bool push_back(element val)
{
if( idata == NPTR ) { // 空表，直接寫入
idata = _alloc(val);
nextof(idata) = NPTR;
return true;
}
if( ifree != NPTR ) { // 非空，先找到最後一個節點
pointer last = idata, np;
while( nextof(last) != NPTR ) last = nextof(last);
np = _alloc(val);
nextof(np) = NPTR;
nextof(last) = np;
return true;
}
return false;
}

// insert val to after p pointed node.
bool insert_after(pointer p, element val)
{
if( ifree != NPTR && p != NPTR ) {
pointer pn = _alloc(val);
nextof(pn) = nextof(p);
nextof(p) = pn;
return true;
}
return false;
}

// insert to the position in front of p.
bool insert(pointer ptr, element val)
{
if( ifree == NPTR ) return false; // 沒有結點，直接返回
if( ptr == idata ) { // 有一個節點
pointer np = _alloc(val);
nextof(np) = idata;
idata = np;
return true;
}
else { // 其他情況，先找 ptr 的前驅，再插入
pointer p = idata;
while( p != NPTR ) {
if( nextof(p) == ptr ) { // find p -- the prev node of ptr.
return insert_after(p, val); // insert val after p.
}
p = nextof(p);
}
}
return false;
}

// find element, return the prev node pointer.
pointer find_prev(element val)
{
pointer p = idata;
while( p != NPTR ) {
if( dataof( nextof(p) ) == val )
return p;
p = nextof(p);
}
return NPTR;
}

// find element, return the node pointer.
pointer find(element val)
{
pointer p = idata;
while( p != NPTR ) {
if( dataof(p) == val ) return p;
p = nextof(p);
}
return NPTR;
}

// pop front element.
void pop_front()
{
if( idata != NPTR ) { // 將 data list 最前面的節點 移到 free list 上
#if 0
pointer p = idata;
idata = nextof(idata); // idata = nextof(idata);
nextof(p) = ifree; // SLList[p].next = ifree;
ifree = p;
#else
pointer p = idata;
idata = nextof(idata);
_free(p);
#endif
}
}

// pop back element.
void pop_back()
{
if( idata == NPTR ) return;
if( nextof(idata) == NPTR ) { // only 1 node.
nextof(idata) = ifree;
ifree = idata;
idata = NPTR;
}
else { // 找到最後一個節點 p，以及它的前驅 q.
// TODO: find the last node p, and it's perv node q.
pointer p = idata, q;
while( nextof(p) != NPTR ) {
q = p;
p = nextof( p );
}
// remove *p to free list, update nextof(q) to NPTR.
nextof(p) = ifree;
ifree = p;
nextof(q) = NPTR;
}
}

void show()
{
pointer p = idata;
for( ; p != NPTR; p = nextof(p) ) {
printf(" %3d ", dataof(p) );
}
printf("\n");
}

#define INFOSHOW
void info()
{
#ifdef INFOSHOW
int i;
DEBUGVAL(ifree);
DEBUGVAL(idata);
puts("====================\n"
"index\tdata\tnext\n"
"--------------------");
for(i=0; i<MAXN; i++) {
printf("%d\t%d\t%d\n", i, SLList[i].data, SLList[i].next);
}
puts("====================\n");
#endif
}

/*
測試程式：
*/
int main()
{
int i;
init();

#if 1 // push_front test:
puts("push_front test:");
for(i=0; i<MAXN+2; i++) {
push_front(2*i+1);
show();
}

puts("pop_front test:");
for(i=0; i<MAXN+2; i++) {
pop_front();
show();
}
#endif

#if 1 // push_back test:
puts("push_back test:");
for(i=0; i<MAXN+2; i++) {
push_back((i+1)*10);
show();
}

puts("pop_back test:");
for(i=0; i<MAXN+1; i++)
{
pop_back();
show();
}
#endif

#if 1 // insert test:
puts("insert test:");
for(i=0; i<MAXN+2; i++)
{
insert(idata, (i+1)*10);
show();
}
puts("clear...\n");
clear();
#endif

#if 1 // insert_after test:
puts("insert_after test:");
push_back(-99);
for(i=0; i<MAXN+1; i++) {
insert_after(idata, i+1);
show();
}
puts("clear...\n");
clear();
#endif

#if 1 // find test:
puts("find test:");
for(i=0; i<MAXN/2; i++) {
push_front(MAXN-i);
push_back(MAXN/2-i);
//show();
}
show();
info();
for(i=0; i<MAXN; i++) {
int val = rand()%(2*MAXN);
pointer p = find(val);
if( p != NPTR )
printf("%3d %3d found at %d\n", val, dataof(p), p);
else
printf("%3d not found\n", val);
}
#endif

#if 1
puts("\nfind_prev test:");
for(i=0; i<MAXN; i++) {
int val = rand()%(2*MAXN);
pointer p = find_prev(val);
if( p != NPTR )
printf("%3d %3d found at %d's next.\n", val, dataof(nextof(p)), p);
else
printf("%3d not found\n", val);
}
#endif

#if 1 // find_prev and insert_after test:
clear();
puts("\nfind_prev and insert_after test:");
for(i=0; i<MAXN/2; i++) {
push_front(MAXN/2-i);
}
show();
for(i=0; i<MAXN/2; i++) {
int val = rand()%(2*MAXN), n=-(i+1);
pointer p = find_prev(val);
if( p != NPTR ) {
printf("insert %d to front of %d:", n, val);
insert_after(p, n);
show();
}
}
#endif

#if 1 // find and insert test:
clear();
puts("\nfind and insert test:");
for(i=0; i<MAXN/2; i++) {
push_front(MAXN/2-i);
}
show();
for(i=0; i<MAXN/2; i++) {
int val = rand()%MAXN, n=-(i+1);
pointer p = find(val);
if( p != NPTR ) {
printf("insert %d to after of %d:", n, val);
insert_after(p, n);
show();
}
}
#endif

puts("end of main().");
return 0;
}

//

測試結果如下：

複製代碼 代碼如下:push_front test:
1
3 1
5 3 1
7 5 3 1
9 7 5 3 1
11 9 7 5 3 1
13 11 9 7 5 3 1
15 13 11 9 7 5 3 1
17 15 13 11 9 7 5 3 1
19 17 15 13 11 9 7 5 3 1
21 19 17 15 13 11 9 7 5 3 1
23 21 19 17 15 13 11 9 7 5 3 1
25 23 21 19 17 15 13 11 9 7 5 3 1
27 25 23 21 19 17 15 13 11 9 7 5 3 1
29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
29 27 25 23 21 19 17 15 13 11 9 7 5 3 1
pop_front test:
27 25 23 21 19 17 15 13 11 9 7 5 3 1
25 23 21 19 17 15 13 11 9 7 5 3 1
23 21 19 17 15 13 11 9 7 5 3 1
21 19 17 15 13 11 9 7 5 3 1
19 17 15 13 11 9 7 5 3 1
17 15 13 11 9 7 5 3 1
15 13 11 9 7 5 3 1
13 11 9 7 5 3 1
11 9 7 5 3 1
9 7 5 3 1
7 5 3 1
5 3 1
3 1
1

push_back test:

20
20 30
20 30 40
20 30 40 50
20 30 40 50 60
20 30 40 50 60 70
20 30 40 50 60 70 80
20 30 40 50 60 70 80 90
20 30 40 50 60 70 80 90 100
20 30 40 50 60 70 80 90 100 110
20 30 40 50 60 70 80 90 100 110 120
20 30 40 50 60 70 80 90 100 110 120 130
20 30 40 50 60 70 80 90 100 110 120 130 140
20 30 40 50 60 70 80 90 100 110 120 130 140 150
20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
20 30 40 50 60 70 80 90 100 110 120 130 140 150 160
pop_back test:
20 30 40 50 60 70 80 90 100 110 120 130 140 150
20 30 40 50 60 70 80 90 100 110 120 130 140
20 30 40 50 60 70 80 90 100 110 120 130
20 30 40 50 60 70 80 90 100 110 120
20 30 40 50 60 70 80 90 100 110
20 30 40 50 60 70 80 90 100
20 30 40 50 60 70 80 90
20 30 40 50 60 70 80
20 30 40 50 60 70
20 30 40 50 60
20 30 40 50
20 30 40
20 30
20

insert test:

10
20 10
30 20 10
40 30 20 10
50 40 30 20 10
60 50 40 30 20 10
70 60 50 40 30 20 10
80 70 60 50 40 30 20 10
90 80 70 60 50 40 30 20 10
100 90 80 70 60 50 40 30 20 10
110 100 90 80 70 60 50 40 30 20 10
120 110 100 90 80 70 60 50 40 30 20 10
130 120 110 100 90 80 70 60 50 40 30 20 10
140 130 120 110 100 90 80 70 60 50 40 30 20 10
150 140 130 120 110 100 90 80 70 60 50 40 30 20 10
150 140 130 120 110 100 90 80 70 60 50 40 30 20 10
150 140 130 120 110 100 90 80 70 60 50 40 30 20 10
clear...

insert_after test:
-99 1
-99 2 1
-99 3 2 1
-99 4 3 2 1
-99 5 4 3 2 1
-99 6 5 4 3 2 1
-99 7 6 5 4 3 2 1
-99 8 7 6 5 4 3 2 1
-99 9 8 7 6 5 4 3 2 1
-99 10 9 8 7 6 5 4 3 2 1
-99 11 10 9 8 7 6 5 4 3 2 1
-99 12 11 10 9 8 7 6 5 4 3 2 1
-99 13 12 11 10 9 8 7 6 5 4 3 2 1
-99 14 13 12 11 10 9 8 7 6 5 4 3 2 1
-99 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
-99 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
-99 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
clear...

find test:
10 11 12 13 14 15 16 8 7 6 5 4 3 2 1
ifree: -1
idata: 14
====================
index data next
--------------------
16 1
8 3
15 0
7 5
14 2
6 7
13 4
5 9
12 6
4 11
11 8
3 13
10 10
2 15
9 12
1 -1
====================
9 found at 14
3 found at 11
not found
4 found at 9
1 found at 15
12 found at 8
not found
14 found at 4
not found
16 found at 0
9 found at 14
not found
not found
not found
9 found at 14
11 found at 10

find_prev test:
not found
6 found at 3's next.
not found
not found
7 found at 1's next.
12 found at 10's next.
not found
not found
4 found at 7's next.
not found
13 found at 8's next.
not found
6 found at 3's next.
not found
7 found at 1's next.
not found

find_prev and insert_after test:
2 3 4 5 6 7 8
insert -4 to front of 8: 1 2 3 4 5 6 7 -4 8
insert -5 to front of 3: 1 2 -5 3 4 5 6 7 -4 8
insert -8 to front of 6: 1 2 -5 3 4 5 -8 6 7 -4 8

find and insert test:
2 3 4 5 6 7 8
insert -2 to after of 3: 1 2 3 -2 4 5 6 7 8
insert -6 to after of 8: 1 2 3 -2 4 5 6 7 8 -6
insert -7 to after of 5: 1 2 3 -2 4 5 -7 6 7 8 -6
end of main().