吴裕雄--天生自然python编程：实例(3)

# 返回 x 在 arr 中的索引，如果不存在返回 -1
def binarySearch (arr, l, r, x): 

    # 基本判断
    if r >= l: 

        mid = int(l + (r - l)/2)

        # 元素整好的中间位置
        if arr[mid] == x:
            return mid 

        # 元素小于中间位置的元素，只需要再比较左边的元素
        elif arr[mid] > x:
            return binarySearch(arr, l, mid-1, x) 

        # 元素大于中间位置的元素，只需要再比较右边的元素
        else:
            return binarySearch(arr, mid+1, r, x) 

    else:
        # 不存在
        return -1

# 测试数组
arr = [ 2, 3, 4, 10, 40 ]
x = 10

# 函数调用
result = binarySearch(arr, 0, len(arr)-1, x) 

if result != -1:
    print ("元素在数组中的索引为 %d" % result )
else:
    print ("元素不在数组中")

def search(arr, n, x): 

    for i in range (0, n):
        if (arr[i] == x):
            return i;
    return -1; 

# 在数组 arr 中查找字符 D
arr = [ 'A', 'B', 'C', 'D', 'E' ];
x = 'D';
n = len(arr);
result = search(arr, n, x)
if(result == -1):
    print("元素不在数组中")
else:
    print("元素在数组中的索引为", result);

def insertionSort(arr): 

    for i in range(1, len(arr)): 

        key = arr[i] 

        j = i-1
        while j >=0 and key < arr[j] :
                arr[j+1] = arr[j]
                j -= 1
        arr[j+1] = key 

arr = [12, 11, 13, 5, 6]
insertionSort(arr)
print ("排序后的数组:")
for i in range(len(arr)):
    print ("%d" %arr[i])

def partition(arr,low,high):
    i = ( low-1 )         # 最小元素索引
    pivot = arr[high]
    for j in range(low , high): 

        # 当前元素小于或等于 pivot
        if   arr[j] <= pivot: 

            i = i+1
            arr[i],arr[j] = arr[j],arr[i] 

    arr[i+1],arr[high] = arr[high],arr[i+1]
    return ( i+1 ) 

# arr[] --> 排序数组
# low  --> 起始索引
# high  --> 结束索引

# 快速排序函数
def quickSort(arr,low,high):
    if low < high: 

        pi = partition(arr,low,high) 

        quickSort(arr, low, pi-1)
        quickSort(arr, pi+1, high) 

arr = [10, 7, 8, 9, 1, 5]
n = len(arr)
quickSort(arr,0,n-1)
print ("排序后的数组:")
for i in range(n):
    print ("%d" %arr[i]),

import sys
A = [64, 25, 12, 22, 11] 

for i in range(len(A)): 

    min_idx = i
    for j in range(i+1, len(A)):
        if A[min_idx] > A[j]:
            min_idx = j 

    A[i], A[min_idx] = A[min_idx], A[i] 

print ("排序后的数组：")
for i in range(len(A)):
    print("%d" %A[i]),

def bubbleSort(arr):
    n = len(arr)

    # 遍历所有数组元素
    for i in range(n):

        # Last i elements are already in place
        for j in range(0, n-i-1):

            if arr[j] > arr[j+1] :
                arr[j], arr[j+1] = arr[j+1], arr[j]

arr = [64, 34, 25, 12, 22, 11, 90]

bubbleSort(arr)

print ("排序后的数组:")
for i in range(len(arr)):
    print ("%d" %arr[i]),

def merge(arr, l, m, r):
    n1 = m - l + 1
    n2 = r- m 

    # 创建临时数组
    L = [0] * (n1)
    R = [0] * (n2)

    # 拷贝数据到临时数组 arrays L[] 和 R[]
    for i in range(0 , n1):
        L[i] = arr[l + i] 

    for j in range(0 , n2):
        R[j] = arr[m + 1 + j] 

    # 归并临时数组到 arr[l..r]
    i = 0     # 初始化第一个子数组的索引
    j = 0     # 初始化第二个子数组的索引
    k = l     # 初始归并子数组的索引

    while i < n1 and j < n2 :
        if L[i] <= R[j]:
            arr[k] = L[i]
            i += 1
        else:
            arr[k] = R[j]
            j += 1
        k += 1

    # 拷贝 L[] 的保留元素
    while i < n1:
        arr[k] = L[i]
        i += 1
        k += 1

    # 拷贝 R[] 的保留元素
    while j < n2:
        arr[k] = R[j]
        j += 1
        k += 1

def mergeSort(arr,l,r):
    if l < r:
        m = int((l+(r-1))/2)
        mergeSort(arr, l, m)
        mergeSort(arr, m+1, r)
        merge(arr, l, m, r) 

arr = [12, 11, 13, 5, 6, 7]
n = len(arr)
print ("给定的数组")
for i in range(n):
    print ("%d" %arr[i]), 

mergeSort(arr,0,n-1)
print ("\n\n排序后的数组")
for i in range(n):
    print ("%d" %arr[i]),

def heapify(arr, n, i):
    largest = i
    l = 2 * i + 1     # left = 2*i + 1
    r = 2 * i + 2     # right = 2*i + 2 

    if l < n and arr[i] < arr[l]:
        largest = l 

    if r < n and arr[largest] < arr[r]:
        largest = r 

    if largest != i:
        arr[i],arr[largest] = arr[largest],arr[i]  # 交换

        heapify(arr, n, largest) 

def heapSort(arr):
    n = len(arr) 

    # Build a maxheap.
    for i in range(n, -1, -1):
        heapify(arr, n, i) 

    # 一个个交换元素
    for i in range(n-1, 0, -1):
        arr[i], arr[0] = arr[0], arr[i]   # 交换
        heapify(arr, i, 0) 

arr = [ 12, 11, 13, 5, 6, 7]
heapSort(arr)
n = len(arr)
print ("排序后")
for i in range(n):
    print ("%d" %arr[i]),

def countSort(arr):
    output = [0 for i in range(256)]
    count = [0 for i in range(256)]
    ans = ["" for _ in arr]
    for i in arr:
        count[ord(i)] += 1
    for i in range(256):
        count[i] += count[i-1]
    for i in range(len(arr)):
        output[count[ord(arr[i])]-1] = arr[i]
        count[ord(arr[i])] -= 1
    for i in range(len(arr)):
        ans[i] = output[i]
    return ans  

arr = "wwwrunoobcom"
ans = countSort(arr)
print ( "字符数组排序 %s"  %("".join(ans)) )

def shellSort(arr):
    n = len(arr)
    gap = int(n/2)
    while gap > 0:
        for i in range(gap,n):
            temp = arr[i]
            j = i
            while  j >= gap and arr[j-gap] >temp:
                arr[j] = arr[j-gap]
                j -= gap
            arr[j] = temp
        gap = int(gap/2)

arr = [ 12, 34, 54, 2, 3] 

n = len(arr)
print ("排序前:")
for i in range(n):
    print(arr[i]), 

shellSort(arr) 

print ("\n排序后:")
for i in range(n):
    print(arr[i]),

from collections import defaultdict 

class Graph:
    def __init__(self,vertices):
        self.graph = defaultdict(list)
        self.V = vertices

    def addEdge(self,u,v):
        self.graph[u].append(v) 

    def topologicalSortUtil(self,v,visited,stack): 

        visited[v] = True

        for i in self.graph[v]:
            if visited[i] == False:
                self.topologicalSortUtil(i,visited,stack) 

        stack.insert(0,v) 

    def topologicalSort(self):
        visited = [False]*self.V
        stack =[] 

        for i in range(self.V):
            if visited[i] == False:
                self.topologicalSortUtil(i,visited,stack) 

        print (stack) 

g= Graph(6)
g.addEdge(5, 2);
g.addEdge(5, 0);
g.addEdge(4, 0);
g.addEdge(4, 1);
g.addEdge(2, 3);
g.addEdge(3, 1); 

print ("拓扑排序结果：")
g.topologicalSort()