Add Bold Tag In String

Link: https://www.lintcode.com/problem/add-bold-tag-in-string/description

class Solution:
    """
    @param s: a string
    @param dict: a list of strings
    @return: return a string
    """
    def add_bold_tag(self, s: str, dict: List[str]) -> str:
        # write your code here
        n=len(s)
        boldarr=[False for i in range(n)]
        for i in dict:
            length=len(i)
            for j in range(n):
                if(s[j:j+length] == i):
                    for k in range(j,j+length):
                        boldarr[k]=True
        
        c=0
        ans=""
        i=0
        while(i<n):
            if(boldarr[i]==False):
                ans=ans+s[i]
                i+=1
            else:
                ans=ans+"<b>"
                while(i<n and boldarr[i]==True):
                    ans=ans+s[i]
                    i+=1
                ans=ans+"</b>"
        return ans