【剑指offer】36.数字在排序数组中出现的次数[by Python]

题目描述：

统计一个数字在排序数组中出现的次数

解法1：

思路：看到排序数组，首先想到的是二分法查找，先找到数字重复出现的左边位置，再找到右边位置，再相减即得到目标值

# -*- coding:utf-8 -*-
class Solution:
    def GetNumberOfK(self, data, k):
        num = 0
        if data:
            first = self.getFirstK(data, k , 0, len(data) - 1)
            last = self.getLastK(data, k, 0, len(data) - 1)
            if first > -1 and last > -1:
                num = last - first + 1
        return num

    def getFirstK(self, data, k, start, end):
        if start > end:
            return -1
        mid = (start + end) / 2
        midD = data[mid]
        if midD > k:
            end = mid - 1
        elif midD < k:
            start = mid + 1
        else:
            if (mid == 0) or (mid > 0 and data[mid - 1] != k):
                return mid
            else:
                end = mid - 1
        return self.getFirstK(data, k, start, end)

    def getLastK(self, data, k, start, end):
        if start > end:
            return -1
        mid = (start + end) / 2
        midD = data[mid]
        if midD > k:
            end = mid - 1
        elif midD < k:
            start = mid + 1
        else:
            if (mid == len(data) - 1) or (mid < len(data) - 1 and data[mid + 1] != k):
                return mid
            else:
                start = mid + 1
        return self.getLastK(data, k, start, end)#复制粘贴搞错了。。
 
 

 
 
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解法2：

class Solution:
    def GetNumberOfK(self, data, k):
        return data.count(k)
 
 

 
 
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解法3：

class Solution:
    def GetNumberOfK(self, data, k):
        num=0
        for i in data:
            if i==k:
                num+=1
        return num
 
 

 
 
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