LeetCode题解——Minimum Window Substring

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".

Note:
If there is no such window in S that covers all characters in T, return the emtpy string "".

If there are multiple such windows, you are guaranteed that there will always be only one unique minimum window in S.

解题思路：首先找到符合条件的一个解如：ADOBEC,大小为6的window再在找到的窗口中看能否缩小范围，比如若此时找到的子窗口为AADOBEC,可缩小范围为ADOBEC，大小为6的window;然后删除第一个数，这里指A,再寻找可能组成的窗口

// Minimum Window Substring.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"
#include 
#include 
using namespace std;

class Solution {
public:
    string minWindow(string s, string t) {
        if (t.empty())
            return "";
        int t_map[256] = {0}, s_map[256] = {0};
        int t_size = 0;

        for (auto c : t)
        {
            if (t_map[c] == 0)
                t_size ++;
            t_map[c] ++;
        }
        int start = 0, end = 0, found = 0, min_start = 0, min_end = s.size() + 1;
        while (start <= end && end <= s.size())
        {
            if (found < t_size)
            {
                end ++;
                char c = s [end - 1];
                if (t_map[c] > 0 && ++s_map[c]  ==  t_map[c])
                {
                    found ++;
                }
            }else {
                start ++;
                char c = s [start - 1];
                if (t_map[c] > 0 && s_map[c]--  ==  t_map[c])
                {
                    found --;
                }
            }
            if (found == t_size && end - start < min_end - min_start)
            {
                min_start = start;
                min_end = end;
            }
        }
        if (min_end == s.size() + 1)
            return "";
        return s.substr(min_start, min_end - min_start);
    }
};


int main(int argc, char** argv)
{
	string S = "AAABCEFAABFC";
	string T = "AABC";
	Solution s;
	string ans=s.minWindow(S,T);
	return 0;
}