swapLexOrder

给定一个字符串str和字符串对应的可以交换位置的下表数组pairs，求交换之后字典顺序最大的字符串(facebook笔试题).
- 题目可能说的不是很明了，看个例子就很清楚要做什么了
- 给定一个字符串str="abcd"，可交换位置的下表数组为pairs=[[1,4],[3,4]],输出结果应该是swapLexOrder(str,pairs)="dbca"
- pairs=[[1,4],[3,4]]告诉我们可以交换的位置是1和4或者3和4之间，这样可以说1,3,，4之间是可以相互交换位置的，然后据此对字符串操作，"cbda","cbad","dbac","dbca"所以交换之后的指定位置按字典顺序排序后的字符串为”dbca".

验证代码(python)

def swapLexOrder(string, pairs):elems = list(string)connected = []for pair in pairs:current_con_ind = -1to_delete_ind = []for j in range(len(connected)):if pair[0] in connected[j] or pair[1] in connected[j]:if current_con_ind == -1:connected[j].extend(pair)connected[j] = sorted(list(set(connected[j])))current_con_ind = jelse:connected[current_con_ind].extend(connected[j])to_delete_ind.append(j)connected[current_con_ind].extend(pair)connected[current_con_ind] = sorted(list(set(connected[current_con_ind])))for d in to_delete_ind:del connected[d]if current_con_ind == -1:connected.append(sorted(pair))print connectedfor indeces in connected:substring = []for index in indeces:substring.append(string[index-1])substring = sorted(substring, reverse=True)for i in range(len(indeces)):elems[indeces[i]-1] = substring[i]return ''.join(elems)

提交代码(C++)

std::string swapLexOrder(std::string str, std::vector<std::vector<int>> pairs) {std::vector<int>del;std::vector<std::set<int>>indeies;for(size_t i=0;i<pairs.size();i++){int flag=-1;for(size_t j=0;j<indeies.size();j++){if(indeies[j].count(pairs[i][0])||indeies[j].count(pairs[i][1])){if(flag==-1){indeies[j].insert(pairs[i][0]);indeies[j].insert(pairs[i][1]);flag=j;}else{for(std::set<int>::iterator it=indeies[j].begin();it!=indeies[j].end();it++){indeies[flag].insert(*it);}del.push_back(j);}}}for(size_t k=0;k<del.size();k++){indeies.erase(indeies.begin()+del[k]-k);}if(flag==-1){std::set<int>oIndex;oIndex.insert(pairs[i][0]);oIndex.insert(pairs[i][1]);indeies.push_back(oIndex);}del.clear();}for(size_t i=0;i<indeies.size();i++){std::vector<char>subStr;for(std::set<int>::iterator it=indeies[i].begin();it!=indeies[i].end();it++){subStr.push_back(str[*it-1]);}sort(subStr.begin(),subStr.end());int j=subStr.size()-1;for(std::set<int>::iterator it=indeies[i].begin();it!=indeies[i].end();it++){str[*it-1]=subStr[j--];}}return str;
}

refer

[1] https://codefights.com/interview-practice/task/5vXzdE9yzjsoMZ9sk

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