检查给定的字符串是否是给定数组的前缀子数组

给定一个字符串str和一个单词数组word[] ，任务是找出str是否是word[]的前缀字符串。

例子：

Input: str = “indiaismycountry”,  
word[] = {“india”, “is”, “my”, “country”, “and”, “i”, “love”, “india”}
Output: true
Explanation: String str can be made by concatenating “india”, “is”, “my” and “country” together.

Input: str = “indianism”,  
word[] = {“india”, “is”, “my”, “country”, “and”, “i”, “love”, “india”}
Output: false
Explanation: It is impossible to make str using the prefixes of the word array.

方法：这是一个简单的实现相关问题。请按照以下步骤操作：

• 取一个名为ans的空字符串。
• 遍历单词数组并继续将单词数组的每个元素添加到ans 。
• 添加到ans后，将其与s进行比较，如果它们都匹配，则返回 true，否则继续。
• 如果迭代结束并且ans与s不匹配，则返回 false。

下面是实现上述方法的 C++ 程序——

C++

// C++ program to implement the
// given approach
#include 
using namespace std;
 
// Function to check weather string
// is prefix
bool isPrefixString(string s,
                    vector& word)
{
    // ans is taken as an empty string
    string ans = "";
 
    // N is used to store
    // the size of word array
    int N = word.size();
 
    // Iterating over the word array
    for (int i = 0; i < N; i++) {
        // Adding element by element
        // of the array
        ans += word[i];
 
        // If ans and str are same
        // return true
        if (ans == s)
            return true;
    }
 
    // As iteration is ending which means
    // string is not prefix so return false.
    return false;
}
 
// Driver code
int main()
{
    string str = "indiaismycountry";
    vector word
        = { "india", "is", "my",
            "country", "and", "i",
            "love", "india" };
    bool ans = isPrefixString(str, word);
    if (ans)
        cout << "True";
    else
        cout << "False";
    return 0;
}

Java

// Java program for the above approach
import java.io.*;
import java.lang.*;
import java.util.*;
 
class GFG {
 
  // Function to check weather string
  // is prefix
  static Boolean isPrefixString(String s,
                                String word[])
  {
     
    // ans is taken as an empty string
    String ans = "";
 
    // N is used to store
    // the size of word array
    int N = word.length;
 
    // Iterating over the word array
    for (int i = 0; i < N; i++) {
      // Adding element by element
      // of the array
      ans += word[i];
      // If ans and str are same
      // return true
      if (ans.equals(s))
        return true;
    }
 
    // As iteration is ending which means
    // string is not prefix so return false.
    return false;
  }
 
  // Driver code
  public static void main (String[] args)
  {
    String str = "indiaismycountry";
    String word[]
      = { "india", "is", "my",
         "country", "and", "i",
         "love", "india" };
    Boolean ans = isPrefixString(str, word);
    if (ans)
      System.out.println("True");
    else
      System.out.println("False");
  }
}
 
// This code is contributed by hrithikgarg03188.

Python

# Pyhton program to implement the
# given approach
 
# Function to check weather string
# is prefix
def isPrefixString(s, word):
 
    # ans is taken as an empty string
    ans = ""
 
    # N is used to store
    # the size of word array
    N = len(word)
 
    # Iterating over the word array
    for i in range(0, N):
 
        # Adding element by element
        # of the array
        ans = ans + (word[i])
 
        # If ans and str are same
        # return true
        if (ans == s):
            return True
 
    # As iteration is ending which means
    # string is not prefix so return false.
    return False
 
# Driver code
str = "indiaismycountry"
word = ["india", "is", "my", "country", "and", "i", "love", "india"]
 
ans = isPrefixString(str, word)
if (ans == True):
    print("True")
else:
    print("False")
 
# This code is contributed by Samim Hossain Mondal.

C#

// C# program for the above approach
using System;
class GFG {
 
  // Function to check weather string
  // is prefix
  static bool isPrefixString(string s,
                             string []word)
  {
 
    // ans is taken as an empty string
    string ans = "";
 
    // N is used to store
    // the size of word array
    int N = word.Length;
 
    // Iterating over the word array
    for (int i = 0; i < N; i++)
    {
 
      // Adding element by element
      // of the array
      ans += word[i];
 
      // If ans and str are same
      // return true
      if (ans.Equals(s))
        return true;
    }
 
    // As iteration is ending which means
    // string is not prefix so return false.
    return false;
  }
 
  // Driver code
  public static void Main ()
  {
    string str = "indiaismycountry";
    string []word
      = { "india", "is", "my",
         "country", "and", "i",
         "love", "india" };
    bool ans = isPrefixString(str, word);
    if (ans)
      Console.WriteLine("True");
    else
      Console.WriteLine("False");
  }
}
 
// This code is contributed by Samim Hossain Mondal.

Javascript

      // JavaScript code for the above approach
 
      // Function to check weather string
      // is prefix
      function isPrefixString(s, word)
      {
       
          // ans is taken as an empty string
          let ans = "";
 
          // N is used to store
          // the size of word array
          let N = word.length;
 
          // Iterating over the word array
          for (let i = 0; i < N; i++)
          {
           
              // Adding element by element
              // of the array
              ans += word[i];
 
              // If ans and str are same
              // return true
              if (ans == s)
                  return true;
          }
 
          // As iteration is ending which means
          // string is not prefix so return false.
          return false;
      }
 
      // Driver code
      let str = "indiaismycountry";
      let word
          = ["india", "is", "my",
              "country", "and", "i",
              "love", "india"];
      let ans = isPrefixString(str, word);
      if (ans)
          document.write("True");
      else
          document.write("False");
 
     // This code is contributed by Potta Lokesh
  

输出

True

时间复杂度： O(N)，N是字数组的大小。
空间复杂度： O(M) 其中 M 是 str 的长度