Given a string S and a string T, find the minimum window in S which will contain all the characters in T in complexity O(n).
For example,
S ="ADOBECODEBANC"
T ="ABC"Minimum window is
"BANC".Note:
If there is no such window in S that covers all characters in T, return the emtpy string"".If there are multiple such windows, you are guaranteed that there will always be only one unique minimum window in S.
算法思路：窗口移动法。 详见这里
本题算法略吊，还是看详解吧。
代码如下：
1 public class Solution { 2 public String minWindow(String s, String t) { 3 if(s == null || t == null) return ""; 4 int[] found = new int[256]; 5 int[] needToFind = new int[256]; 6 for(int i = 0; i < t.length(); i++){ 7 needToFind[t.charAt(i)]++; 8 } 9 int start = 0, count = 0,minWin = Integer.MAX_VALUE; 10 String res = ""; 11 for(int i = 0; i < s.length(); i++){ 12 if(needToFind[s.charAt(i)] == 0) continue; 13 char c = s.charAt(i); 14 found[c]++; 15 if(found[c] <= needToFind[c]) 16 count++; 17 if(count == t.length()){ 18 //move the begin pointer while the constrain meets 19 while(start < s.length() && ( needToFind[s.charAt(start)] == 0 || found[s.charAt(start)] > needToFind[s.charAt(start)])){ 20 if(found[s.charAt(start)] > 0) 21 found[s.charAt(start)]--; 22 start++; 23 } 24 //update the min according to the current window 25 if(i - start + 1 < minWin){ 26 minWin = i - start + 1; 27 res = s.substring(start,i + 1); 28 } 29 } 30 } 31 return res; 32 } 33 }
参考：
http://www.cnblogs.com/jdflyfly/p/3815275.html
[leetcode]Minimum Window Substring,布布扣,bubuko.com
[leetcode]Minimum Window Substring
原文：http://www.cnblogs.com/huntfor/p/3915288.html