Open wittyResry opened 8 years ago
INSERT-SORT(A)
for j <- 2 to length(A)
do key <- A[j]
i <- j - 1
while i > 0 and A[i] > key
do A[i+1] <- A[i]
i <- i - 1
A[i+1] <- key
SELECTION-SORT(A)
for j <- 1 to length(A) - 1
do key <- A[j]
idx <- j
i <- j
while i to length(A) and A[i] < key
if A[i+1] <- A[i]
key <- A[i]
idx <- i
i <- i + 1
swap(a[j], a[idx])
MERGE-SORT(A, p, r)
if (p < r)
do q = (p + r) / 2
MERGE-SORT(A, p, q)
MERGE-SORT(A, q+1, r)
MERGE(A, p, q, r)
MERGE(A, p, q, r)
n1 <- q - p + 1
n2 <- r - q
for i <- 1 to n1
do L[i] <- A[p + i - 1]
for j <- 1 to n2
do R[j] <- A[q + j]
L[n1 + 1] <- oo
L[n2 + 1] <- oo
i <- 1
j <- 1
for k <- p to r
if L[i] <= R[j]
A[k] = L[i]
i <- i + 1
else
A[k] = R[j]
j <- j + 1
思考:
分治算法:
1 分解(将原问题分解成一系列子问题);
2 合并(递归地解各子问题);
3. 合并(将子问题的结果合并成原问题的解)
BUBBLE-SORT(A)
for i <- 1 to length(A)
do for j <- length(A) downto i+1
do if A[j] < A[j-1]
then exchange(A[j], A[j-1])
MAX-HEAPIFY(A, i)
l = LEFT(i);
r = RIGHT(i);
if l <= HEAP-SIZE(A) and A[l] > A[i]
then largest = l
else largest = i
if r <= HEAP-SIZE(A) and A[r] > A[largest]
then largest = r
if largest != i
then exchange A[i] <-> A[largest]
MAX-HEAPIFY(A, largest)
BUILD-MAX-HEAD(A)
HEAD-SIZE(A) = length[A]
for i <- length[A] downto 1
do MAX-HEAPIFY(A, i)
HEAPSORT(A)
BUILD-MAX-HEAP(A)
for i <- length(A) downto 2
do exchange A[1] <-> A[i]
HEAP-SIZE(A) = HEAP-SIZE(A) - 1
MAX-HEAPIFY(A, 1)
PARENT(i)
return i/2
LEFT(i)
return 2*i
RIGHT(i)
return 2*i+1
QUICKSORT(A, p, r)
if p < r
then q = PARTITION(A, p, r)
QUICKSORT(A, p, q - 1)
QUICKSORT(A, q + 1, r)
PARTITION(A, p, r)
x <- A[r]
i <- p - 1
for j <- p to r - 1
do if A[j] <= x
then i = i + 1
exchange A[i] <-> A[j]
exchange A[i+1] <-> A[r]
return i + 1
思考:快速排序的时间复杂度如何证明?提示:数学期望,因为各个元素仅与主元素进行比较,并且在某次比较PARTITION调用结束以后,该次调用中所有用到的主元素就不会与其他任何其他元素进行比较了。
思考:排序时间的下界证明?提示:决策树模型
COUNTING-SORT(A, B, k)
for i <- 0 to k
do C[i] = 0
for j <- 1 to length(A)
do C[A[j]] = C[A[j]] + 1
for i <- 1 to k
do C[i] = C[i] + C[i - 1]
//C[i] 表示有C[i]个元素小于等于i
for j <- length(A) downto 1
do B[C[A[j]]] = A[j]
C[A[j]] = C[A[j]] - 1
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