LeetCode#648 Replace Words (week14)

week14

题目

In English, we have a concept called root, which can be followed by some other words to form another longer word - let’s call this word successor. For example, the root an, followed by other, which can form another word another.

Now, given a dictionary consisting of many roots and a sentence. You need to replace all the successor in the sentence with the root forming it. If a successor has many roots can form it, replace it with the root with the shortest length.

You need to output the sentence after the replacement.



Note:

The input will only have lower-case letters.

1 <= dict words number <= 1000

1 <= sentence words number <= 1000

1 <= root length <= 100

1 <= sentence words length <= 1000

原题地址：https://leetcode.com/problems/replace-words/description/

解析

题目给出一个数组dict作为存放字典中的字符串，给定一个字符串sentence，要求将sentence以空格分解为子字符串，如果某个子字符串a以dict中的某个字符串b为开头，称b为a的root，用b代替sentence中对应的a，最后将sentence中的子字符串重新连接为一个字符串

大致思路是先将sentence按空格分割为子字符串并存放在数组中，对于每个子字符串，查找dict中是否有字符串是其root，有则以之代替，最后用数组中的字符串及空格重新拼接成新的字符串

代码

class Solution {
public:
string replaceWords(vector<string>& dict, string sentence) {
vector<string> words;
spilt(sentence, words);
replace(dict, words);

string rel = "";
for (int i = 0; i < words.size(); ++i) {
rel += words[i];
rel += " ";
}
return rel.substr(0,rel.size() - 1);
}
/*将字符串按空格分解*/
void spilt(string sentence, vector<string>& words) {
int len = sentence.size();
int begin = 0, end = 0;
int last_blank = -1;
while (end < len) {
/*每找到一个空格生成一个子串*/
if (sentence[end] != ' ') {
++end;
}
else {
last_blank = end;
string ss = sentence.substr(begin, end - begin);
words.push_back(ss);
begin = end + 1;
end = begin;
}
}
/*最后一个子串后面没有空格，单独处理*/
if (last_blank != -1) {
string s = sentence.substr(last_blank + 1, len - last_blank);
words.push_back(s);
}

}
/*对于words中的每个字符串，在dict中查找root并替代*/
void replace(vector<string>& dict, vector<string>& words) {
int len = words.size();
for (int i = 0; i < len; ++i) {
for (int j = 0; j < dict.size(); ++j) {
if (isRoot(dict[j], words[i])) {
words[i] = dict[j];
break;
}
}
}
}
/*比较得到字符串str是否以sub开头*/
bool isRoot(string sub, string str) {
int k = 0, j = 0;
while (str[k] == sub[j] && k < str.size() - 1) {
if (j == sub.size() - 1) {
return true;
}
++k;
++j;
}
return false;
}
};