76.窗口滑动最小子串

Minimum Window Substring

问题描述：

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).For example,S = "ADOBECODEBANC"T = "ABC"Minimum window is "BANC".

参考答案（c++）：

class Solution {public:    string minWindow(string s, string t) {        vector<int> map(128,0);        for(auto c: t) map[c]++;        int counter=t.size(), begin=0, end=0, d=INT_MAX, head=0;        while(end<s.size()){            if(map[s[end++]]-->0) counter--; //in t            while(counter==0){ //valid                if(end-begin<d)  d=end-(head=begin);                if(map[s[begin++]]++==0) counter++;  //make it invalid            }          }        return d==INT_MAX? "":s.substr(head, d);            }};

性能：

参考答案（python）：

class Solution(object):    def minWindow(self, s, t):        need, missing = collections.Counter(t), len(t)        i = I = J = 0        for j, c in enumerate(s, 1):            missing -= need[c] > 0            need[c] -= 1            if not missing:                while i < j and need[s[i]] < 0:                    need[s[i]] += 1                    i += 1                if not J or j - i <= J - I:                    I, J = i, j        return s[I:J]

性能：