【LeetCode】#76最小覆盖子串(Minimum Window Substring)

【LeetCode】#76最小覆盖子串(Minimum Window Substring)

题目描述

给定一个字符串 S 和一个字符串 T，请在 S 中找出包含 T 所有字母的最小子串。

示例

输入: S = “ADOBECODEBANC”, T = “ABC”
输出: “BANC”

Description

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”

解法

class Solution {
    public String minWindow(String s, String t) {
        Map<Character, Integer> map = new HashMap<>();
        int min = Integer.MAX_VALUE;
        int minStart = 0, minEnd = 0;
        int count = t.length();
        for(char c : t.toCharArray()){
            map.put(c, map.containsKey(c) ? map.get(c)+1 : 1);
        }
        int left = 0;
        for(int right=0; right<s.length(); right++){
            char val = s.charAt(right);
            if(map.containsKey(val)){
                map.put(val, map.get(val)-1);
                if(map.get(val)>=0){
                    count--;
                }
            }
            while(count==0){
                if(right-left<min){
                    min = right-left;
                    minStart = left;
                    minEnd = right;
                }
                char temp = s.charAt(left);
                if(map.containsKey(temp)){
                    map.put(temp, map.get(temp)+1);
                    if(map.get(temp)>0) count++;
                }
                left++;
            }
        }
        return min == Integer.MAX_VALUE ? "" : s.substring(minStart, minEnd+1);
    }
}