检查堆栈或队列中的移动是否可能

给定一个二进制数组，其中 1 表示推送操作，0 表示堆栈或队列中的弹出操作。任务是检查可能的操作集是否有效。
例子：

Input: a[] = {1, 1, 0, 0, 1} 
Output: Valid 
Input : a[] = {1, 1, 0, 0, 0} 
Output : Invalid 
The third pop operation cannot be done as the stack or queue will be empty at that moment of time. 

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一种幼稚的做法是使用堆栈或队列，当数组元素为1时执行入栈操作，当数组元素为0时执行出栈操作。当有出栈操作时，则移动无效如果堆栈或队列为空。如果我们可以执行所有操作，那么这些动作是有效的。
时间复杂度：O(N)
辅助空间：O(N)
一种有效的方法是计算推送操作并在执行弹出操作时减少它们。如果在任何实例期间，计数变为小于 0，则操作集无效。
下面是上述方法的实现。

C++

// C++ program to Check if moves in a stack
// or queue are possible or not
#include 
using namespace std;
 
// Function to check if
// operations are valid or not
bool check(int a[], int n)
{
 
    // count number of push operations
    int ones = 0;
 
    // traverse in the array
    for (int i = 0; i < n; i++) {
 
        // push operation
        if (a[i])
            ones++;
 
        // pop operation
        else
            ones--;
 
        // if at any moment pop() operations
        // exceeds the number of push operations
        if (ones < 0)
            return false;
    }
 
    return true;
}
 
// Driver Code
int main()
{
    int a[] = { 1, 1, 0, 0, 1 };
    int n = sizeof(a) / sizeof(a[0]);
    if (check(a, n))
        cout << "Valid";
    else
        cout << "Invalid";
}

Java

// Java program to Check if moves in a stack
// or queue are possible or not
 
public class GFG {
 
// Function to check if
// operations are valid or not
    static boolean check(int a[], int n) {
 
        // count number of push operations
        int ones = 0;
 
        // traverse in the array
        for (int i = 0; i < n; i++) {
 
            // push operation
            if (a[i] ==1) {
                ones++;
            } // pop operation
            else {
                ones--;
            }
 
            // if at any moment pop() operations
            // exceeds the number of push operations
            if (ones < 0) {
                return false;
            }
        }
 
        return true;
    }
 
// Driver Code
    static public void main(String[] args) {
        int a[] = {1, 1, 0, 0, 1};
        int n = a.length;
        if (check(a, n)) {
            System.out.println("Valid");
        } else {
            System.out.println("Invalid");
        }
 
    }
}
// This code is contributed by Rajput-Ji

Python 3

# Python 3 program to Check if moves
# in a stack or queue are possible or not
 
# Function to check if
# operations are valid or not
def check(a, n):
 
    # count number of push operations
    ones = 0;
 
    # traverse in the array
    for i in range (0, n):
 
        # push operation
        if (a[i]):
            ones = ones + 1;
 
        # pop operation
        else:
            ones = ones - 1;
 
        # if at any moment pop() operations
        # exceeds the number of push operations
        if (ones < 0):
            return False;
 
    return True;
 
# Driver Code
a = [ 1, 1, 0, 0, 1 ];
n = len(a);
if (check(a, n)):
    print("Valid");
else:
    print("Invalid");
 
# This code is contributed
# by Akanksha Rai

C#

using System;
                     
     
// C# program to Check if moves in a stack
// or queue are possible or not
  
public class GFG {
  
// Function to check if
// operations are valid or not
    static bool check(int []a, int n) {
  
        // count number of push operations
        int ones = 0;
  
        // traverse in the array
        for (int i = 0; i < n; i++) {
  
            // push operation
            if (a[i] ==1) {
                ones++;
            } // pop operation
            else {
                ones--;
            }
  
            // if at any moment pop() operations
            // exceeds the number of push operations
            if (ones < 0) {
                return false;
            }
        }
  
        return true;
    }
  
// Driver Code
    static public void Main() {
        int []a = {1, 1, 0, 0, 1};
        int n = a.Length;
        if (check(a, n)) {
            Console.Write("Valid");
        } else {
            Console.Write("Invalid");
        }
  
    }
}
// This code is contributed by Rajput-Ji

Javascript

 
// JavaScript program to Check if moves in a stack
// or queue are possible or not
 
  
 
    // Function to check if
    // operations are valid or not
    function check(a , n) {
 
        // count number of push operations
        var ones = 0;
 
        // traverse in the array
        for (i = 0; i < n; i++) {
 
            // push operation
            if (a[i] == 1) {
                ones++;
            } // pop operation
            else {
                ones--;
            }
 
            // if at any moment pop() operations
            // exceeds the number of push operations
            if (ones < 0) {
                return false;
            }
        }
 
        return true;
    }
 
    // Driver Code
        var a = [ 1, 1, 0, 0, 1 ];
        var n = a.length;
        if (check(a, n)) {
            document.write("Valid");
        } else {
            document.write("Invalid");
        }
 
 
// This code is contributed by todaysgaurav
 

输出：

Valid

时间复杂度：O(N)
辅助空间：O(1)