question: public String reverseWords ( String s ) { if ( s == null || s . length ( ) == 0 ) return "" ; String res = "" ; for ( int i = 0 ; i < s . length ( ) ; i ++ ) { char c = s . charAt ( i ) ; if ( c == ' ' ) continue ; else { StringBuilder word = new StringBuilder ( ) ; while ( i < s . length ( ) ) { c = s . charAt ( i ) ; if ( c == ' ' ) break ; word . append ( c ) ; i ++ ; } res = res . length ( ) == 0 ? word . toString ( ) : word . toString ( ) + " " + res ; i -- ; } } return res ; }
target:  If space, continue If not, get the word and insert to the front of result note that result may not contain spaces before or after