#coding=utf-8

"""求最長公共子串"""
def lcsubstr(str1,str2):
    dp = [[0 for i in xrange(str2.__len__()+1)] for i in xrange(str1.__len__()+1)]
    count = 0
    index = 0
    for i in xrange(str1.__len__()):
        for j in xrange(str2.__len__()):
            if str1[i] == str2[j]:
                dp[i+1][j+1] = dp[i][j]+1
                if dp[i+1][j+1] > count:
                    count = dp[i+1][j+1]
                    index = i+1
    return str1[index-count:index],count
print lcsubstr('caomamile','jincao')

"""求最長公共子序列"""
def lcsequence(str1,str2):
    match = [ [0 for i in xrange(str2.__len__()+1)] for j in xrange(str2.__len__()+1)]
    dp = [ [0 for i in xrange(str2.__len__()+1)] for j in xrange(str1.__len__()+1)]
    for i in xrange(str1.__len__()):
        for j in xrange(str2.__len__()):
            if str1[i] == str2[j]:
                dp[i+1][j+1] = dp[i][j]+1
            else:
                dp[i+1][j+1] = max(dp[i][j+1],dp[i+1][j])
    retls = []
    row,col = dp.__len__()-1,dp[0].__len__()-1
    while row>0 and col>0:  ###逆轉找最長公共子序列，如果str1[i] = str2[j],將str[i] 加入；如果不等，比較dp[i-1][j] 和 dp[i][j-1]之間的最大值
        if str1[row-1] == str2[col-1]:
            retls.append(str1[row-1])
            row-=1
            col-=1
        else:
            if dp[row-1][col] > dp[row][col-1]:
                row-=1
            else:
                col-=1
    print retls

    return dp[-1][-1]
print lcsequence('13456778','357486782')