正向_逆向匹配分词

Posted 2021-01-18 hapyygril

# 1、统计分词词典，确定词典中最长词条的字符m；
# 2、从左向右取待切分语句的m个字符作为匹配字段，查找词典，如果匹配成功，则作为一个切分后的词语，
#    否则，去掉待匹配字符的最后一个继续查找词典，重复上述步骤直到切分出所有词语。



dictA = [‘南京市‘, ‘南京市长‘, ‘长江大桥‘,  ‘大桥‘]

maxDictA = max([len(word) for word in dictA])

sentence = "南京市长江大桥"

def cutA(sentence):
    result = []
    sentenceLen = len(sentence)
    n = 0

    while n < sentenceLen:
        matched = 0

        for i in range(maxDictA, 0, -1):


            piece = sentence[n:n+i]

            if piece in dictA:
                result.append(piece)
                matched = 1
                n = n + i
                break
        if not matched:

            result.append(sentence[n])
            n += 1

    print(result)

cutA(sentence)  # [‘南京市长‘, ‘江‘, ‘大桥‘]

dictB = [‘南京市‘, ‘南京市长‘, ‘长江大桥‘,  ‘大桥‘]

maxDictB = max([len(word) for word in dictA])

sentence = "南京市长江大桥"
def cutB(sentence):
    result = []
    sentenceLen = len(sentence)

    while sentenceLen > 0:
        word = ‘‘
        for i in range(maxDictB, 0, -1):
            piece = sentence[sentenceLen-i:sentenceLen]
            if piece in dictB:
                word = piece
                result.append(word)
                sentenceLen -= i
                break

        if word is ‘‘:
            sentenceLen -= 1
            result.append(sentence[sentenceLen])

    print(result[::-1])

cutB(sentence)  # [‘南京市‘, ‘长江大桥‘]

# 双向最大匹配法
# 思想： 将正向最大匹配和逆向匹配得到的分词结果进行比较，按照最大匹配原则，选择切分总词数最少的作为最终分词结果。