???學院的保送研究生復試馬上就要開始了，復試中最能拉開距離的就是筆試，這也是我發(fā)揮個人能力的地方。為了萬無一失，我準備這幾天復習一下數(shù)據(jù)結(jié)構(gòu)，今天復習的內(nèi)容是排序算法。
???一般的排序算法大體上分為三類——插入排序、交換排序和選擇排序。
???插入排序的基本思想是將第N個記錄插入到前面(N-1)個有序的記錄當中。直接插入排序、折半插入排序和系爾排序都是屬于插入排序。
???直接插入排序：
?1
void
?InsertSort(RcdType?r[],
int
?n)
?2
{
?3
????
int
?i,j;
?4
????
for
(i
=
2
;i
<=
n;i
++
)
{
?5
????????r[
0
]
=
r[i];
?6
????????j
=
i
-
1
;
?7
????????
while
(r[
0
].key
<
r[j].key)
{
?8
????????????r[j
+
1
]
=
r[j];
?9
????????????j
--
;
10
????????}
11
????????r[j
+
1
]
=
r[
0
];
12
????}
????
13
}
???折半插入排序：
?1
void
?BinSort(RcdType?r[],
int
?n)
?2
{
?3
????
int
?i,j,mid,low,high;
?4
????
for
(i
=
2
;i
<=
n;i
++
)
{
?5
????????r[
0
]
=
r[i];
?6
????????low
=
1
;
?7
????????high
=
i
-
1
;
?8
????????
while
(low
<=
high)
{
?9
????????????mid
=
(low
+
high)
/
2
;
10
????????????
if
(r[
0
].key
<
r[mid].key)?high
=
mid
-
1
;
11
????????????
else
?low
=
mid
+
1
;
12
????????}
13
????????
for
(j
=
i
-
1
;j
>=
low;j
--
)?
14
????????????r[j
+
1
]
=
r[j];
15
????????r[low]
=
r[
0
];
16
????}
17
}
???交換排序算法的基本思想是按照某種順序比較兩個記錄的關(guān)鍵字大小，然后根據(jù)需要交換兩個記錄的位置。冒泡排序和快速排序都是屬于交換排序。
???冒泡排序：
?1
void
?BubbleSort(RcdType?r[],
int
?n)
?2
{
?3
????
int
?i,j,flag;
?4
????
for
(i
=
1
;i
<
n;i
++
)
{
?5
????????flag
=
1
;
?6
????????
for
(j
=
1
;j
<=
n
-
i;j
++
)
{
?7
????????????
if
(r[j
+
1
].key
<
r[j].key)
{
?8
????????????????falg
=
0
;
?9
????????????????r[
0
]
=
r[j];
10
????????????????r[j]
=
r[j
+
1
];
11
????????????????r[j
+
1
]
=
r[
0
];
12
????????????}
13
????????}
14
????????
if
(flag)?
break
;
15
????}
16
}
???快速排序：
?1
void
?QuickSort(RcdType?r[],
int
?low,
int
?high)
?2
{
?3
????
int
?i,j;
?4
????i
=
low;
?5
????j
=
high;
?6
????r[
0
]
=
r[i];
?7
????
while
(i
<
j)
{
?8
????????
while
(i
<
j?
&&
?r[j].key
>=
r[
0
].key)?j
--
;
?9
????????
if
(i
<
j)?r[i
++
]
=
r[j];
10
????????
while
(i
<
j?
&&
?r[i].key
<=
r[
0
].key)?i
++
;
11
????????
if
(i
<
j)?r[j
--
]
=
r[
0
];
12
????}
13
????r[i]
=
r[
0
];
14
????
if
(low
<
i
-
1
)?QuickSort(r,low,i
-
1
);
15
????
if
(high
>
i
+
1
)?QuickSort(r,i
+
1
,high);
16
}
???選擇排序算法的思想是根據(jù)某中方法選擇一個關(guān)鍵字最大的記錄或者關(guān)鍵字最小的記錄，放到適當?shù)奈恢谩：唵芜x擇排序和堆排序都是屬于選擇排序算法。
???簡單選擇排序：
?1
void
?SelectSort(RcdType?r[],
int
?n)
?2
{
?3
????
int
?i,j,p;
?4
????
for
(i
=
1
;i
<
n;i
++
)
{
?5
????????p
=
i;
?6
????????
for
(j
=
i
+
1
;j
<=
n;j
++
)
{
?7
????????????
if
(r[j].key
<
r[p].key)?p
=
j;
?8
????????}
?9
????????
if
(p
!=
i)
{
10
????????????r[
0
]
=
r[p];
11
????????????r[p]
=
r[i];
12
????????????r[i]
=
r[
0
];
13
????????}
14
????}
15
}
???堆排序：
?1
void
?Heap(RcdType?r[],
int
?i,
int
?m)
?2
{
?3
????
int
?j;
?4
????j
=
2
*
i;
?5
????r[
0
]
=
r[i];
?6
????
while
(j
<=
m)
{
?7
????????
if
(j
<
m?
&&
?r[j
+
1
].key
<
r[j].key)?j
++
;
?8
????????
if
(r[j].key
<
r[
0
].key)
{
?9
????????????r[i]
=
r[j];
10
????????????i
=
j;
11
????????????j
=
i
*
2
;
12
????????}
else
{
13
????????????j
=
m
+
1
;
14
????????}
15
????}
16
????r[i]
=
r[
0
];
17
}
18
19
void
?HeapSort(RcdType?r[],
int
?n)
20
{
21
????
int
?i,j;
22
????
//
初始化堆
23
????
for
(i
=
n
/
2
;i
>=
1
;i
--
)
{
24
????????Heap(r,i,n);
25
????}
26
????
//
輸出
27
????
for
(i
=
n;i
>=
1
;i
--
)
{
28
????????printf(
"
%d\t
"
,r[
1
].key);
29
????????r[
1
]
=
r[i];
30
????????Heap(r,
1
,i
-
1
);
31
????}
32
}
?