Minimum Window Substring

問題描述：

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".

參考答案（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);        
    }
};

效能：

參考答案（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]

效能：