📜  实现文本编辑器的撤消和重做功能

📅  最后修改于: 2021-09-06 05:57:45             🧑  作者: Mango

给定一个字符串数组Q[] ,由以下类型的查询组成:

  • “WRITE X”:在文档中写入一个字符X。
  • “UNDO”:删除对文档所做的最后更改。
  • “REDO”:恢复最近对文档执行的UNDO操作。
  • “READ”:读取并打印文件的内容。

例子:

方法:使用Stack可以解决这个问题。请按照以下步骤解决问题:

  • 初始化两个堆栈,比如UndoRedo
  • 遍历字符串数组Q ,并执行以下操作:
  • 如果遇到“WRITE”字符串,则将字符推送到撤消堆栈
  • 如果遇到“UNDO”字符串,则从Undo堆栈中弹出顶部元素并将其推送到Redo堆栈。
  • 如果遇到“REDO”字符串,则弹出重做堆栈的顶部元素并将其压入撤消堆栈。
  • 如果遇到“READ”字符串,则以相反的顺序打印Undo堆栈的所有元素。

下面是上述方法的实现:

C++
// C++ Program to implement
// the above approach
#include 
using namespace std;
 
// Function to perform
// "WRITE X" operation
void WRITE(stack& Undo,
           char X)
{
    // Push an element to
    // the top of stack
    Undo.push(X);
}
 
// Function to perform
// "UNDO" operation
void UNDO(stack& Undo,
          stack& Redo)
{
    // Stores top element
    // of the stack
    char X = Undo.top();
 
    // Erase top element
    // of the stack
    Undo.pop();
 
    // Push an element to
    // the top of stack
    Redo.push(X);
}
 
// Function to perform
// "REDO" operation
void REDO(stack& Undo,
          stack& Redo)
{
    // Stores the top element
    // of the stack
    char X = Redo.top();
 
    // Erase the top element
    // of the stack
    Redo.pop();
 
    // Push an element to
    // the top of the stack
    Undo.push(X);
}
 
// Function to perform
// "READ" operation
void READ(stack Undo)
{
    // Store elements of stack
    // in reverse order
    stack revOrder;
 
    // Traverse Undo stack
    while (!Undo.empty()) {
        // Push an element to
        // the top of stack
        revOrder.push(Undo.top());
 
        // Erase top element
        // of stack
        Undo.pop();
    }
 
    while (!revOrder.empty()) {
        // Print the top element
        // of the stack
        cout << revOrder.top();
      Undo.push(revOrder.top());
 
        // Erase the top element
        // of the stack
        revOrder.pop();
    }
 
    cout << " ";
}
 
// Function to perform the
// queries on the document
void QUERY(vector Q)
{
    // Stores the history of all
    // the queries that have been
    // processed on the document
    stack Undo;
 
    // Stores the elements
    // of REDO query
    stack Redo;
 
    // Stores total count
    // of queries
    int N = Q.size();
 
    // Traverse all the query
    for (int i = 0; i < N; i++) {
        if (Q[i] == "UNDO") {
            UNDO(Undo, Redo);
        }
        else if (Q[i] == "REDO") {
            REDO(Undo, Redo);
        }
        else if (Q[i] == "READ") {
            READ(Undo);
        }
        else {
            WRITE(Undo, Q[i][6]);
        }
    }
}
 
// Driver Code
int main()
{
 
    vector Q = { "WRITE A", "WRITE B",
                         "WRITE C", "UNDO",
                         "READ", "REDO", "READ" };
    QUERY(Q);
    return 0;
}


Python3
# Python Program to implement
# the above approach
global Undo
global Redo
 
# Stores the history of all
# the queries that have been
# processed on the document
Undo = []
 
# Stores the elements
# of REDO query
Redo = []
 
# Function to perform
# "WRITE X" operation
def WRITE(Undo, X):
 
    # Push an element to
    # the top of stack
    Undo.append(X)
 
# Function to perform
# "UNDO" operation
def UNDO(Undo, Redo):
 
    # Stores top element
    # of the stack
    X = Undo[-1]
 
    # Erase top element
    # of the stack
    Undo.pop()
 
    # Push an element to
    # the top of stack
    Redo.append(X)
 
# Function to perform
# "REDO" operation
def REDO(Undo, Redo):
 
    # Stores the top element
    # of the stack
    X = Redo[-1]
 
    # Erase the top element
    # of the stack
    Redo.pop()
 
    # Push an element to
    # the top of the stack
    Undo.append(X)
 
# Function to perform
# "READ" operation
def READ(Undo):
    print(*Undo, sep = "",
          end = " ")
 
# Function to perform the
# queries on the document
def QUERY(Q):
 
    # Stores total count
    # of queries
    N = len(Q)
 
    # Traverse all the query
    for i in range(N):
        if(Q[i] == "UNDO"):
            UNDO(Undo, Redo)
        elif(Q[i] == "REDO"):
            REDO(Undo, Redo)
        elif(Q[i] == "READ"):
            READ(Undo)
        else:
            WRITE(Undo, Q[i][6])
 
# Driver Code
Q = ["WRITE A", "WRITE B", "WRITE C",
     "UNDO", "READ", "REDO", "READ"]
QUERY(Q)
 
#This code is contributed by avanitrachhadiya2155


输出:
AB ABC

时间复杂度:
撤销: O(1)
重做: O(1)
写: O(1)
READ: (N),其中N表示Undo栈的大小
辅助空间: O(N)

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