最短摘要

public class ShortDigest {private HashMap<String, Integer> map = new HashMap<String, Integer>();//保存最短摘要的起始和结束位置。private Point shortest = new Point();public ShortDigest(String[] keys){for(String key : keys){map.put(key, 0);}}public String getShortDigest(String[] ss){assert(true);updateShortest(ss, 0, 0);int i = shortest.x;int j = shortest.y;String result = "";for(int k=i; k<=j; k++){result += ss[k] + " ";}return result;}/** * 两个指针，代表头尾， 先移动尾指针至满足要求，再移动头指针，缩小范围。 * 然后递归至结束。 * @param ss * @param start * @param end */private void updateShortest(String[] ss, int start, int end){int i = start;int j = end;if(j >= ss.length-1){return;}while(!isAllKeys()){j++;if(j==ss.length){return;}if(isKey(ss[j])){map.put(ss[j], map.get(ss[j])+1);}}while(isAllKeys()){if(isKey(ss[i])){map.put(ss[i], map.get(ss[i])-1);}i++;}int current = j-i+2;if((shortest.length==0) || (shortest.length>current)){shortest.set(i-1, j);}updateShortest(ss, i, j);}private boolean isAllKeys(){for(String key : map.keySet()){int v = map.get(key);if(v == 0){return false;}}return true;}public boolean isKey(String s){return map.containsKey(s);}public class Point{public int x;public int y;public int length;public void set(int x, int y){this.x = x;this.y = y;length = y-x+1;}}/** * @param args */public static void main(String[] args) {// TODO Auto-generated method stubString s = "Online retailer book of book movies music and games item along with electronics toys book apparel " +"sports tools of groceries and general home and garden item";String[] ss = s.split("\\s");String[] keys = {"book", "item", "of"};ShortDigest sd = new ShortDigest(keys);String res = sd.getShortDigest(ss);System.out.println(res);}}