How to find smallest substring which contains all characters from a given string?

Question

I have recently come across an interesting question on strings. Suppose you are given following:

Input string1: \"this is a test string\"
Input strin         


        

Answer 1

I received the same interview question. I am a C++ candidate but I was in a position to code relatively fast in JAVA.

Java [Courtesy : Sumod Mathilakath]

import java.io.*;
import  java.util.*;

class UserMainCode
{


    public String GetSubString(String input1,String input2){
        // Write code here...
        return find(input1, input2);
    }
  private static boolean containsPatternChar(int[] sCount, int[] pCount) {
        for(int i=0;i<256;i++) {
            if(pCount[i]>sCount[i])
                return false;
        }
        return true;
    }
  public static String find(String s, String p) {
        if (p.length() > s.length())
            return null;
        int[] pCount = new int[256];
        int[] sCount = new int[256];
        // Time: O(p.lenght)
        for(int i=0;i

C++ [Courtesy : sundeepblue]

#include 
#include 
#include 
#include 
using namespace std;
string find_minimum_window(string s, string t) {
    if(s.empty() || t.empty()) return;

    int ns = s.size(), nt = t.size();
    vector total(256, 0);
    vector sofar(256, 0);
    for(int i=0; i total[c]) {
                    sofar[c]--;
                    L++;
                }
                else break;
            }  
            if(R - L + 1 < min_win_len) {   // this judge should be inside POS1
                min_win_len = R - L + 1;
                minL = L;
            }
        }
    }
    string res;
    if(count == nt)                         // gist3, cannot forget this. 
        res = s.substr(minL, min_win_len);  // gist4, start from "minL" not "L"
    return res;
}
int main() {
    string s = "abdccdedca";
    cout << find_minimum_window(s, "acd");
}

Erlang [Courtesy : wardbekker]

-module(leetcode).

-export([min_window/0]).

%% 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.



min_window() ->
    "eca" = min_window("cabeca", "cae"),
    "eca" = min_window("cfabeca", "cae"),
    "aec" = min_window("cabefgecdaecf", "cae"),
    "cwae" = min_window("cabwefgewcwaefcf", "cae"),
    "BANC" = min_window("ADOBECODEBANC", "ABC"),
    ok.

min_window(T, S) ->
    min_window(T, S, []).

min_window([], _T, MinWindow) ->
    MinWindow;
min_window([H | Rest], T, MinWindow) ->
    NewMinWindow = case lists:member(H, T) of
                       true ->
                           MinWindowFound = fullfill_window(Rest, lists:delete(H, T), [H]),
                           case length(MinWindow) == 0 orelse (length(MinWindow) > length(MinWindowFound)
                               andalso length(MinWindowFound) > 0) of
                               true ->
                                   MinWindowFound;
                               false ->
                                   MinWindow
                           end;
                       false ->
                           MinWindow
                   end,
    min_window(Rest, T, NewMinWindow).

fullfill_window(_, [], Acc) ->
    %% window completed
    Acc;
fullfill_window([], _T, _Acc) ->
    %% no window found
    "";
fullfill_window([H | Rest], T, Acc) ->
    %% completing window
    case lists:member(H, T) of
        true ->
            fullfill_window(Rest, lists:delete(H, T), Acc ++ [H]);
        false ->
            fullfill_window(Rest, T, Acc ++ [H])
    end.

REF:

• http://articles.leetcode.com/finding-minimum-window-in-s-which/#comment-511216
• http://www.mif.vu.lt/~valdas/ALGORITMAI/LITERATURA/Cormen/Cormen.pdf