力扣：30. 串联所有单词的子串

import org.omg.CORBA.StringHolder;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * @author xnl
 * @Description:
 * @date: 2022/6/23   22:32
 */
public class Solution {
    public static void main(String[] args) {
        Solution solution = new Solution();
        String s = "barfoothefoobarman";
        String[] words = {"foo","bar"};
        System.out.println(solution.findSubstring2(s, words));
    }

    public List<Integer> findSubstring(String s, String[] words) {
        // 存储单词个数
        Map<String, Integer> map = new HashMap<>();
        for (String word : words) {
            map.put(word, map.getOrDefault(word, 0) + 1);
        }
        int n = s.length(), m = words.length, k = words[0].length();
        // 结果
        List<Integer> res = new ArrayList<>();
        out: for (int i = 0; i + m * k <= n; i++){
            Map<String, Integer> cur = new HashMap<>();
            String substring = s.substring(i, i + m * k);
            for (int j = 0; j < substring.length(); j += k){
                String item = substring.substring(j, j + k);
                if (!map.containsKey(item)){
                    continue out;
                }
                cur.put(item, cur.getOrDefault(item, 0) + 1);
            }
            if (cur.equals(map)){
                res.add(i);
            }
        }
        return res;
    }

    public List<Integer> findSubstring2(String s, String[] words) {
        int n = s.length(), m = words.length, k = words[0].length();
        List<Integer> list = new ArrayList<>();
        Map<String, Integer> map = new HashMap<>();
        for (String word :words){
            map.put(word, map.getOrDefault(word, 0 ) + 1);
        }

        for (int i = 0; i < k; i++){
            Map<String, Integer> cur = new HashMap<>();
            for (int j = i; j + k <= n; j += k){
                String temp = s.substring(j, j + k);
                cur.put(temp, cur.getOrDefault(temp, 0) + 1);
                if (j >= i + (m * k)){
                    int idx = j - m * k;
                    String prev = s.substring(idx, idx + k);
                    if (cur.get(prev) == 1){
                        cur.remove(prev);
                    } else {
                        cur.put(prev, cur.get(prev) - 1);
                    }
                    if (!cur.getOrDefault(prev, 0).equals(map.getOrDefault(prev, 0))) {
                        continue;
                    }
                }
                if (!cur.getOrDefault(temp, 0).equals(map.getOrDefault(temp, 0))){
                    continue;
                }
                if (cur.equals(map)){
                    list.add(j - (m - 1) * k);
                }
            }
        }
        return list;
    }
}