public class Solution {
	public String minWindow(String S, String T) {
	    if(T.isEmpty() || S.isEmpty()) {
	        return "";
	    }
	    int tcount = 0;
	    int minLen = Integer.MAX_VALUE;
	    int[] needToFind = new int[128];
	    int[] hasFound = new int[128];
	    for(int i=0; i<T.length(); i++) {
	        int c = T.charAt(i);
	        needToFind[c]++;
	    }
	    int l = 0, r = 0;
	    int minl = 0, minr = 0;
	    for(; r<S.length(); r++) {
	        int rc = S.charAt(r);
	        if(needToFind[rc] > 0) {
	            hasFound[rc]++;
	            if(needToFind[rc] >= hasFound[rc]) {
	                tcount++;
	            }
	            if(tcount == T.length()) {
	                int lc = S.charAt(l);
	                while(needToFind[lc] == 0 || needToFind[lc] < hasFound[lc]) {
	                    if(needToFind[lc] < hasFound[lc]) {
	                        hasFound[lc]--;
	                    }
	                    l++;
	                    lc = S.charAt(l);
	                }
	                if(r - l + 1 < minLen) {
	                    minr = r;
	                    minl = l;
	                    minLen = r - l + 1;
	                }
	            }
	        }
	    }
	    if(tcount != T.length()) {
	        return "";
	    } else {
	        return S.substring(minl, minr+1);
	    }
	}
}