types = list(set([i[-1] for i in end]))#提取end列表中每个字符串元素的最后一个字符，将其转换为列表 type = request.args.get('num')

这段代码是用来生成一个列表，列表中的元素是来自另一个列表（end）中每个元素的最后一个字符，并且去重。

具体地说，代码先通过列表推导式从end中取出每个元素的最后一个字符，然后用set()函数去重得到一个集合，接着再用list()函数转换成列表赋值给types变量。最终得到的types列表中元素是不重复的，并且每个元素都是来自end列表中某个元素的最后一个字符。

相关问题

编写一个程序实现LR(1)项目集及状态转换图构造、LR(1)分析表构造、并实现在利用LR(1)分析表分析字符串同时生成逆波兰式

以下是一个基于Java实现的LR(1)语法分析程序，包括LR(1)项目集及状态转换图构造、LR(1)分析表构造和利用LR(1)分析表分析字符串同时生成逆波兰式的功能。程序中使用了JavaCC工具生成LR(1)语法分析器。

LR1Parser.jj：

options {
  STATIC = false;
}

PARSER_BEGIN(LR1Parser)
package com.example.lr1parser;
import java.util.*;
PARSER_END(LR1Parser)

// Define terminals
TOKEN : {
  <PLUS: "+"> |
  <MINUS: "-"> |
  <TIMES: "*"> |
  <DIV: "/"> |
  <LPAREN: "("> |
  <RPAREN: ")"> |
  <NUM: (["0"-"9"])+>
}

// Define non-terminals
void start() : {} {
  expression()
}

void expression() : {} {
  term() ( <PLUS> term() )*
}

void term() : {} {
  factor() ( <TIMES> factor() )*
}

void factor() : {} {
  <NUM> |
  <LPAREN> expression() <RPAREN>
}

// Define LR(1) items
List<Item> items = new ArrayList<Item>();
Item startItem = new Item(new Production("S", "E"), 0, "$");
items.add(startItem);

// Define LR(1) item set
Set<ItemSet> itemSetSet = new HashSet<ItemSet>();

// Define LR(1) transition table
Map<ItemSet, Map<String, ItemSet>> transitionTable = new HashMap<ItemSet, Map<String, ItemSet>>();

// Define LR(1) action table
Map<ItemSet, Map<String, Action>> actionTable = new HashMap<ItemSet, Map<String, Action>>();

// Define LR(1) goto table
Map<ItemSet, Map<String, ItemSet>> gotoTable = new HashMap<ItemSet, Map<String, ItemSet>>();

// Define stack for parsing
Stack<ItemSet> stack = new Stack<ItemSet>();
Stack<String> input = new Stack<String>();

// Define output queue for reverse polish notation
Queue<String> outputQueue = new LinkedList<String>();

// Define state counter for generating state IDs
int stateCounter = 0;

// Define action types
enum ActionType {
  SHIFT,
  REDUCE,
  ACCEPT,
  ERROR
}

// Define action
class Action {
  ActionType type;
  int stateOrProduction;

  public Action(ActionType type, int stateOrProduction) {
    this.type = type;
    this.stateOrProduction = stateOrProduction;
  }
}

// Define item
class Item {
  Production production;
  int dot;
  String lookahead;

  public Item(Production production, int dot, String lookahead) {
    this.production = production;
    this.dot = dot;
    this.lookahead = lookahead;
  }

  public boolean isReduceItem() {
    return dot == production.getRight().size();
  }

  public String getNextSymbol() {
    if (isReduceItem()) {
      return null;
    }
    return production.getRight().get(dot);
  }

  public Item getNextItem() {
    if (isReduceItem()) {
      return null;
    }
    return new Item(production, dot + 1, lookahead);
  }

  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append(production.getLeft());
    sb.append(" ->");
    for (int i = 0; i < production.getRight().size(); i++) {
      if (i == dot) {
        sb.append(" .");
      }
      sb.append(" ");
      sb.append(production.getRight().get(i));
    }
    if (dot == production.getRight().size()) {
      sb.append(" .");
    }
    sb.append(", ");
    sb.append(lookahead);
    return sb.toString();
  }
}

// Define item set
class ItemSet {
  int id;
  Set<Item> items = new HashSet<Item>();

  public ItemSet() {
    this.id = stateCounter++;
  }

  public ItemSet(Set<Item> items) {
    this.id = stateCounter++;
    this.items = items;
  }

  public void addItem(Item item) {
    items.add(item);
  }

  public Set<String> getLookaheads(String symbol) {
    Set<String> lookaheads = new HashSet<String>();
    for (Item item : items) {
      if (!item.isReduceItem() && item.getNextSymbol().equals(symbol)) {
        lookaheads.add(item.lookahead);
      }
    }
    return lookaheads;
  }

  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("I" + id + ":\n");
    for (Item item : items) {
      sb.append("  " + item + "\n");
    }
    return sb.toString();
  }
}

// Define production
class Production {
  String left;
  List<String> right;

  public Production(String left, String... right) {
    this.left = left;
    this.right = Arrays.asList(right);
  }

  public String getLeft() {
    return left;
  }

  public List<String> getRight() {
    return right;
  }

  public boolean isNullable() {
    for (String symbol : right) {
      if (!isNullable(symbol)) {
        return false;
      }
    }
    return true;
  }

  public static boolean isNullable(String symbol) {
    return symbol.equals("$") || symbol.equals("ε");
  }

  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append(left);
    sb.append(" ->");
    for (String symbol : right) {
      sb.append(" ");
      sb.append(symbol);
    }
    return sb.toString();
  }
}

// Generate LR(1) items
void generateItems() {
  for (Production production : Productions.productions) {
    for (int i = 0; i <= production.getRight().size(); i++) {
      for (String lookahead : Productions.first(production.getRight().subList(i, production.getRight().size()))) {
        Item item = new Item(production, i, lookahead);
        items.add(item);
      }
    }
  }
}

// Generate LR(1) item set closure
ItemSet closure(ItemSet itemSet) {
  ItemSet closure = new ItemSet(itemSet.items);
  boolean changed = true;
  while (changed) {
    changed = false;
    Set<Item> newItems = new HashSet<Item>();
    for (Item item : closure.items) {
      String nextSymbol = item.getNextSymbol();
      if (nextSymbol != null) {
        for (Item i : items) {
          if (i.production.getLeft().equals(nextSymbol) && Productions.first(i.production.getRight()).contains(item.lookahead)) {
            Item newItem = new Item(i.production, 0, item.lookahead);
            if (!closure.items.contains(newItem)) {
              newItems.add(newItem);
            }
          }
        }
      }
    }
    if (!newItems.isEmpty()) {
      closure.items.addAll(newItems);
      changed = true;
    }
  }
  return closure;
}

// Generate LR(1) item set goto
ItemSet goTo(ItemSet itemSet, String symbol) {
  Set<Item> newItems = new HashSet<Item>();
  for (Item item : itemSet.items) {
    String nextSymbol = item.getNextSymbol();
    if (nextSymbol != null && nextSymbol.equals(symbol)) {
      newItems.add(item.getNextItem());
    }
  }
  return closure(new ItemSet(newItems));
}

// Generate LR(1) item set family
void generateItemSetFamily() {
  ItemSet startItemSet = closure(new ItemSet(Collections.singleton(startItem)));
  itemSetSet.add(startItemSet);
  boolean changed = true;
  while (changed) {
    changed = false;
    Set<ItemSet> newSets = new HashSet<ItemSet>();
    for (ItemSet itemSet : itemSetSet) {
      for (String symbol : Productions.getAllSymbols()) {
        ItemSet newItemSet = goTo(itemSet, symbol);
        if (!newItemSet.items.isEmpty() && !itemSetSet.contains(newItemSet)) {
          newSets.add(newItemSet);
          changed = true;
        }
      }
    }
    if (!newSets.isEmpty()) {
      itemSetSet.addAll(newSets);
    }
  }
}

// Generate LR(1) transition table
void generateTransitionTable() {
  for (ItemSet itemSet : itemSetSet) {
    Map<String, ItemSet> transitionMap = new HashMap<String, ItemSet>();
    for (String symbol : Productions.getAllSymbols()) {
      ItemSet newItemSet = goTo(itemSet, symbol);
      if (!newItemSet.items.isEmpty()) {
        transitionMap.put(symbol, newItemSet);
      }
    }
    transitionTable.put(itemSet, transitionMap);
  }
}

// Generate LR(1) action table
void generateActionTable() {
  for (ItemSet itemSet : itemSetSet) {
    Map<String, Action> actionMap = new HashMap<String, Action>();
    for (Item item : itemSet.items) {
      if (item.isReduceItem()) {
        if (item.production.getLeft().equals("S")) {
          actionMap.put("$", new Action(ActionType.ACCEPT, 0));
        } else {
          for (String lookahead : Productions.follow(item.production.getLeft())) {
            actionMap.put(lookahead, new Action(ActionType.REDUCE, Productions.getProductionIndex(item.production)));
          }
        }
      } else {
        String nextSymbol = item.getNextSymbol();
        if (nextSymbol != null) {
          ItemSet nextStateSet = transitionTable.get(itemSet).get(nextSymbol);
          actionMap.put(nextSymbol, new Action(ActionType.SHIFT, nextStateSet.id));
        }
      }
    }
    for (String symbol : Productions.getAllSymbols()) {
      if (!actionMap.containsKey(symbol)) {
        actionMap.put(symbol, new Action(ActionType.ERROR, -1));
      }
    }
    actionTable.put(itemSet, actionMap);
  }
}

// Generate LR(1) goto table
void generateGotoTable() {
  for (ItemSet itemSet : itemSetSet) {
    Map<String, ItemSet> gotoMap = new HashMap<String, ItemSet>();
    for (String symbol : Productions.getAllNonTerminals()) {
      ItemSet newItemSet = goTo(itemSet, symbol);
      if (!newItemSet.items.isEmpty()) {
        gotoMap.put(symbol, newItemSet);
      }
    }
    gotoTable.put(itemSet, gotoMap);
  }
}

// Parse input string and generate reverse polish notation
void parse(String inputStr) {
  stack.clear();
  input.clear();
  outputQueue.clear();

  stack.push(itemSetSet.iterator().next());
  input.push("$");
  for (int i = inputStr.length() - 1; i >= 0; i--) {
    input.push(String.valueOf(inputStr.charAt(i)));
  }

  while (true) {
    ItemSet state = stack.peek();
    String symbol = input.peek();
    Action action = actionTable.get(state).get(symbol);
    switch (action.type) {
      case SHIFT:
        stack.push(transitionTable.get(state).get(symbol));
        input.pop();