LeetCode-76-Minimum Window Substring

最新推荐文章于 2024-02-04 10:03:05 发布

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最新推荐文章于 2024-02-04 10:03:05 发布

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原文链接：http://www.cnblogs.com/nobodywang/p/10372839.html

本文详细解析了如何使用滑动窗口算法寻找包含特定字符的最小子串，通过具体实例展示了算法的设计与实现过程。

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算法描述：

Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).

Example:

Input: S = "ADOBECODEBANC", T = "ABC"
Output: "BANC"

Note:

If there is no such window in S that covers all characters in T, return the empty string "".
If there is such window, you are guaranteed that there will always be only one unique minimum window in S.

解题思路：子字符串问题，可以采用强大的滑动窗口方法解决。首先用map对字符串进行映射，并用两个指针分别指向窗口左边和右边，通过不断的滑动两个指针实现对窗口内字符的操作。

    string minWindow(string s, string t) {
        string res = "";
        unordered_map<char,int> map;
        for(char c:t) map[c]++;
        int left=0;
        int right = 0;
        int distance = INT_MAX;
        int count = t.size();
        int head = 0;
        while(right < s.size()){
            if(map[s[right++]]-- >0) count--;
            while(count==0){
                if(right-left< distance){
                    head = left;
                    distance = right-head;
                }
                if(map[s[left++]]++ ==0) count++;
            }
        }
        return distance==INT_MAX?"":s.substr(head,distance);
    }