[Leetcode] 616. Add Bold Tag in String 解题报告

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本文介绍了一种算法，用于在给定字符串中为字典中出现的子串添加加粗标签( 和 )。讨论了如何处理重叠和相邻子串，并提供了具体的代码实现。

题目：

Given a string s and a list of strings dict, you need to add a closed pair of bold tag  and  to wrap the substrings in s that exist in dict. If two such substrings overlap, you need to wrap them together by only one pair of closed bold tag. Also, if two substrings wrapped by bold tags are consecutive, you need to combine them.

Example 1:

Input: 
s = "abcxyz123"
dict = ["abc","123"]
Output:
"<b>abc</b>xyz<b>123</b>"

Example 2:

Input: 
s = "aaabbcc"
dict = ["aaa","aab","bc"]
Output:
"<b>aaabbc</b>c"

Note:

The given dict won't contain duplicates, and its length won't exceed 100.
All the strings in input have length in range [1, 1000].

思路：

很常规的思路：找出dict中的每个单词在s中的出现区段interval，然后将这些intervals进行merge，merge之后形成的不重合的intervals就是我们需要插入或者的地方。

当然本题目也可以用很牛逼的KMP算法实现，时间复杂度应该会更低。可是太难了，还是用简单的吧。

代码：

class Solution {
public:
    string addBoldTag(string s, vector<string>& dict) {
        vector<pair<int, int>> ranges = findPairs(s, dict);
        ranges = merge(ranges);
        for (auto it = ranges.rbegin(); it != ranges.rend(); ++it) {
            s.insert(it->second, "</b>");
            s.insert(it->first, "<b>");
        }
        return s;
    }
private:
    vector<pair<int, int>> findPairs(string &s, vector<string> &dict) {
        vector<pair<int, int>> res;
        for (string w : dict) {
            int n = w.size();
            for (int i = 0; (i = s.find(w, i)) != string::npos; ++i) {
                res.push_back(pair<int, int>(i, i + n));
            }
        }
        return res;
    }
    vector<pair<int ,int>> merge(vector<pair<int, int>> &a) {
        vector<pair<int, int>> r;
        sort(a.begin(), a.end(), compare);
        for (int i = 0, j = -1; i < a.size(); ++i) {
            if (j < 0 || a[i].first > r[j].second) {
                r.push_back(a[i]);
                ++j;
            }
            else {
                r[j].second = max(r[j].second, a[i].second);
            }
        }
        return r;
    }
    static bool compare(pair<int, int> &a, pair<int, int> &b) {
        return a.first < b.first || a.first == b.first && a.second < b.second;
    }
};