题解 | #牛牛的串联子串游戏#

import java.util.*;


public class Solution {
    /**
     * 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
     *
     *
     * @param s string字符串
     * @param words string字符串一维数组
     * @return int整型一维数组
     */
    public int[] findSubstring (String s, String[] words) {
        // write code here
        int n = s.length();
        if (s.isEmpty() || words.length == 0) {
            return new int[0];
        }
        HashMap<String, Integer> map = new HashMap<>();
        for (String word : words) {
            map.put(word, map.getOrDefault(word, 0) + 1);
        }
        List<Integer> list = new ArrayList<>();
        int wordLen = words[0].length();
        int subStrLen = words.length * words[0].length();
        for (int i = 0; i <= n - subStrLen; i++) {
            HashMap<String, Integer> windowMap = new HashMap<>(map);
            int j = i;
            while (j < n) {
                String word = s.substring(j, j + wordLen);
                if (windowMap.containsKey(word)) {
                    int cnt = windowMap.get(word);
                    if (cnt == 1) {
                        windowMap.remove(word);
                    } else {
                        windowMap.put(word, cnt - 1);
                    }
                    j += wordLen;
                } else {
                    break;
                }
            }
            if (windowMap.isEmpty()) {
                list.add(i);
            }
        }

        int[] res = new int[list.size()];
        for (int i = 0; i < list.size(); i++) {
            res[i] = list.get(i);
        }
        return res;
    }
}