LeetCode: Minimum Window Substring

自己写的large没过，用了map，然后用了很多erase, iterator的，懂得一个道理，map这玩意比较慢，尽量少用，在用网上答案的时候没有给数组初始化为0就过不了

class Solution {
public:
    string minWindow(string S, string T) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        int tag[256] = {0};
        int mark[256] = {0};
        int chars, count, head, beg;
        chars = count = head = 0;
        beg = -1;
        int min_w = INT_MAX;
        for (int i = 0; i < T.size(); i++) {
            if (!tag[T[i]]) chars++;
            tag[T[i]]++;
        }
        for (int i = 0; i < S.size(); i++) {
            if (!tag[S[i]]) continue;
            mark[S[i]]++;
            if (mark[S[i]] == tag[S[i]]) count++;
            if (chars == count) {
                while (!tag[S[head]] || mark[S[head]] > tag[S[head]]) {
                    mark[S[head]]--;
                    head++;
                }
                if (i-head < min_w) {
                    min_w = i-head;
                    beg = head;
                }
            }
        }
        if (beg == -1) return "";
        else return S.substr(beg, min_w+1);
    }
};

 C#

public class Solution {
    public string MinWindow(string s, string t) {
        int[] tag = new int[256];
        int[] mark = new int[256];
        int chars = 0, count = 0, head = 0, beg = -1;
        int min_w = Int32.MaxValue;
        for (int i = 0; i < t.Length; i++) {
            if (tag[t[i]] == 0) chars++;
            tag[t[i]]++;
        }
        for (int i = 0; i < s.Length; i++) {
            if (tag[s[i]] == 0) continue;
            mark[s[i]]++;
            if (mark[s[i]] == tag[s[i]]) count++;
            if (chars == count) {
                while (tag[s[head]] == 0 || mark[s[head]] > tag[s[head]]) {
                    mark[s[head]]--;
                    head++;
                }
                if (i - head < min_w) {
                    min_w = i - head;
                    beg = head;
                }
            }
        }
        if (beg == -1) return "";
        else return s.Substring(beg, min_w + 1);
    }
}