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;
}
}