leetcode 71: Substring with Concatenation of All Words

Substring with Concatenation of All WordsFeb 24 '12

You are given a string, S, and a list of words, L, that are all of the same length. Find all starting indices of substring(s) in S that is a concatenation of each word in L exactly once and without any intervening characters.

For example, given:
S: "barfoothefoobarman"
L: ["foo", "bar"]

You should return the indices: [0,9].
(order does not matter).

public class Solution {    public ArrayList<Integer> findSubstring(String S, String[] L) {        // Start typing your Java solution below        // DO NOT write main() function        ArrayList<Integer> res = new ArrayList<Integer>();        if(L.length<1 || S.length() < L.length*L[0].length() ) return res;                    Map<String, Integer> map = new HashMap<String,Integer>();                for(int i=0; i<L.length;i++) {            if( map.containsKey( L[i] ) ) {                map.put( L[i], map.get(L[i])+1) ;            } else {                map.put(L[i], 1);            }        }                int i=0;        int Slen = S.length();        int Llen = L.length;        int sz = L[0].length();                while( Slen-i >= Llen*sz){                        Map<String, Integer> temp = new HashMap<String,Integer>(map);            for(int j=0; j<Llen; j++) {                String sub = S.substring(i+j*sz, i+(j+1)*sz);                                if( temp.containsKey(sub) ) {                    int x = temp.get(sub);                    if( x>1)                         temp.put(sub, temp.get(sub)-1);                    else if( x==1)                         temp.remove( sub);                }else                     break;            }            if(temp.isEmpty() ) res.add(i);                     ++i;        }        return res;    }}