【LeetCode-面试算法经典-Java实现】【030-Substring with Concatenation of All Words（串联所有单词的子串）】

【030-Substring with Concatenation of All Words（串联所有单词的子串）】

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【LeetCode-面试算法经典-Java实现】【所有题目目录索引】

原题

　　You are given a string, s, and a list of words, words, that are all of the same length. Find all starting indices of substring(s) in s that is a concatenation of each word in words exactly once and without any intervening characters.
　　For example, given:
　　s: "barfoothefoobarman"
　　words: ["foo", "bar"]
　　You should return the indices: [0,9].
　　(order does not matter).

题目大意

　　给定一个字符串s和一个字符串数组words，wrods中的字符串长度都相等，找出s中所有的子串恰好包含words中所有字符各一次，返回子串的起始位置。

解题思路

　　把words转化为一个HashMap

代码实现

算法实现类

import java.util.*;public class Solution {    public List<Integer> findSubstring(String s, String[] words) {        List<Integer> list = new ArrayList<Integer>();        if (words.length == 0) return list;        int wLen = words[0].length();        int len = s.length();        if (len < wLen * words.length) return list;        Map<String, Integer> mapW = new HashMap<String, Integer>();        for (String word : words)            mapW.put(word, mapW.containsKey(word) ? mapW.get(word) + 1 : 1);        for (int start = 0; start < wLen; start++) {            int pos = start;            int tStart = -1;            Map<String, Integer> mapT = new HashMap<String, Integer>(mapW);            while (pos + wLen <= len) {                String cand = s.substring(pos, pos + wLen);                if (!mapW.containsKey(cand)) {                    if (tStart != -1) mapT = new HashMap<String, Integer>(mapW);                    tStart = -1;                } else if (mapT.containsKey(cand)) {                    tStart = tStart == -1 ? pos : tStart;                    if (mapT.get(cand) == 1) mapT.remove(cand);                    else mapT.put(cand, mapT.get(cand) - 1);                    if (mapT.isEmpty()) list.add(tStart);                } else {                    while (tStart < pos) {                        String rCand = s.substring(tStart, tStart + wLen);                        if (cand.equals(rCand)) {                            tStart += wLen;                            if (mapT.isEmpty()) list.add(tStart);                            break;                        }                        tStart += wLen;                        mapT.put(rCand, mapT.containsKey(rCand) ? mapT.get(rCand) + 1 : 1);                    }                }                pos += wLen;            }        }        return list;    }}

评测结果

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特别说明

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