堆的定义:n个元素的序列{k1,k2,ki,…,kn}当且仅当满足下关联时,称之为堆。(引荐进修:Python视频教程)
"ki<=k2i,ki<=k2i+1;或ki>=k2i,ki>=k2i+1.(i=1,2,…,[n/2])"
这是规范的堆的定义,然则python 中并没有自力的堆范例,只是包括一些堆操纵函数的模块(heapq =heap+queue首字母),实在堆在python中属于一种特别的列表;
简朴的引见一下heapq中的要领
import heapq 1.heapq.heappush(heap,item) #heap为定义堆,item 增添的元素; eg. heap=[] heapq.heappush(heap, 2) 2.heapq.heapify(list) #将列表转换为堆 eg. list=[5,8,0,3,6,7,9,1,4,2] heapq.heapify(list) 3.heapq.heappop(heap) #删除最小的值 eg. heap=[2, 4, 3, 5, 7, 8, 9, 6] heapq.heappop(heap) ---->heap=[3, 4, 5, 7, 9, 6, 8] 4.heapq.heapreplace(heap, item) #删除最小元素值,增加新的元素值 eg. heap=[2, 4, 3, 5, 7, 8, 9, 6] heapq.heapreplace(heap, 11) ------>heap=[2, 3, 4, 6, 8, 5, 7, 9, 11] 5.heapq.heappushpop(heap, item) #首推断增加元素值与堆的第一个元素值对照,假如大于则删除最小元素,然后增加新的元素值,否则不变动堆 eg. 前提:item >heap[0] heap=[2, 4, 3, 5, 7, 8, 9, 6] heapq.heappushpop(heap, 9)---->heap=[3, 4, 5, 6, 8, 9, 9, 7] 前提:item heap=[2, 4, 3, 5, 7, 8, 9, 6] heapq.heappushpop(heap, 9)---->heap=[2, 4, 3, 5, 7, 8, 9, 6] 6.heapq.merge(...) #将多个堆兼并 7.heapq.nlargest (n, heap) #查询堆中的最大元素,n示意查询元素个数 eg. heap=[2, 3, 5, 6, 4, 8, 7, 9] heapq.nlargest (1, heap)--->[9] 8.heapq.nsmallest(n, heap) #查询堆中的最小元素,n示意查询元素个数 eg. heap=[2, 3, 5, 6, 4, 8, 7, 9] heapq.nlargest (1, heap)--->[2]
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