最小化从给定源到达目的地所需的字符串定义的步骤

给定字符串str和四个整数X ₁ ， Y ₁ ， X ₂和Y ₂ ，其中(X ₁ ，Y ₁ )表示源坐标，而(X ₂ ，Y ₂ )表示目标坐标。给定字符串str ，任务是找到从源到达目标所需的以下四种类型的最小步数：

• 如果str [i] =’E’：将(X ₁ ，Y ₁ )转换为(X ₁ +1，Y ₁ )。
• 如果str [i] =’W’：将(X ₁ ，Y ₁ )转换为(X ₁ – 1，Y ₁ )。
• 如果str [i] =’N’：将(X ₁ ，Y ₁ )转换为(X ₁ ，Y ₁ +1)。
• 如果str [i] =’S’：将(X ₁ ，Ysub> 1)转换为(X ₁ ，Y ₁ – 1)。

如果无法到达目的地，请打印-1 。
注意：不必始终使用str [i]并且可以跳过。但是跳过的字符将添加到所使用的步骤中。例子

Input: str = “SESNW”, x1 = 0, y1 = 0, x2 = 1, y2 = 1 
Output: 4 
Explanation: 
To move from (0, 0) to (1, 1), it requires one ‘E’ and one ‘N’. 
Therefore, the path defined by the substring “SESN” ensures that the destination is reached {(0, 0) -> skip S -> E(1, 0) -> skip S -> (1, 1)}. 
Therefore, the minimum length of the string traversed is 4. 

Input: str = “NNNNNNNN”, x1 = 1, y1 = 1, x2 = 1, y2 = 2 
Output: 1 
Explanation: 
From current position (1, 1) it can move to co-ordinate (1, 2) using first ‘N’ direction. 
Therefore, the minimum length of the string traverse is 1. 

方法：想法是遍历字符串并执行移动直到到达目的地。步骤如下：

1. 初始化四个变量pos1，pos2，pos3和pos4 ，分别存储E，W，N，S的位置。
2. 现在，检查(x1，y1)是否等于(x2，y2)，那么当前位置已经是目的地，因此打印0 。
3. 否则，遍历字符串并检查以下四个条件：
   • 如果x2> x1，则进行迭代直到出现‘E’并更新pos1中的索引。
   • 如果x2 则进行迭代，直到出现“ W”并更新pos2中的索引。
   • 如果y2> y1，则进行迭代，直到出现“ N”并更新pos3中的该索引。
   • 如果y2 则进行迭代，直到出现“ S”并更新pos4中的索引。
4. 执行上述操作后，检查x1！= x2和y1！= y2，然后打印“ -1” ，这意味着无法到达目的地。
5. 否则，找到pos1，pos2，pos3和pos4的最大值并打印。

下面是上述方法的实现：

C++

// C++ program for the above approach
 
#include 
using namespace std;
 
// Function to find the minimum length
// of string required to reach from
// source to destination
void minimum_length(int x1, int y1,
                    int x2, int y2,
                    string str)
{
    // Size of the string
    int n = str.size();
 
    // Stores the index of the four
    // directions E, W, N, S
    int pos1, pos2, pos3, pos4;
    pos1 = -1;
    pos2 = -1;
    pos3 = -1;
    pos4 = -1;
 
    // If destination reached
    if (x1 == x2 && y1 == y2) {
        cout << 0 << endl;
    }
 
    // Iterate over the string
    else {
        for (int i = 0; i < n; i++) {
 
            // Move east
            if (x2 > x1) {
 
                // Change x1 according
                // to direction E
                if (str[i] == 'E') {
                    x1 = x1 + 1;
                    if (x1 == x2) {
                        pos1 = i;
                    }
                }
            }
 
            // Move west
            if (x2 < x1) {
 
                // Change x1 according
                // to direction W
                if (str[i] == 'W') {
                    x1 = x1 - 1;
                    if (x1 == x2) {
                        pos2 = i;
                    }
                }
            }
 
            // Move north
            if (y2 > y1) {
 
                // Change y1 according
                // to direction N
                if (str[i] == 'N') {
                    y1 = y1 + 1;
                    if (y1 == y2) {
                        pos3 = i;
                    }
                }
            }
 
            // Move south
            if (y2 < y1) {
 
                // Change y1 according
                // to direction S
                if (str[i] == 'S') {
                    y1 = y1 - 1;
                    if (y1 == y2) {
                        pos4 = i;
                    }
                }
            }
        }
 
        int z;
        // Store the max of all positions
        z = max(max(max(pos1, pos2),
                    pos3),
                pos4);
 
        // Print the minimum length of
        // string required
        if (x1 == x2 && y1 == y2) {
            cout << z + 1 << endl;
        }
 
        // Otherwise, it is impossible
        else {
            cout << "-1" << endl;
        }
    }
}
 
// Driver Code
int main()
{
    // Given string
    string str = "SESNW";
 
    // Given source and destination
    int x1 = 0, x2 = 1, y1 = 0, y2 = 1;
 
    // Function Call
    minimum_length(x1, y1, x2, y2, str);
    return 0;
}

Java

// Java program for the above approach
import java.util.*;
import java.lang.*;
import java.io.*;
 
class GFG{
 
// Function to find the minimum length
// of string required to reach from
// source to destination
static void minimum_length(int x1, int y1,
                           int x2, int y2,
                           String str)
{
     
    // Size of the string
    int n = str.length();
   
    // Stores the index of the four
    // directions E, W, N, S
    int pos1, pos2, pos3, pos4;
    pos1 = -1;
    pos2 = -1;
    pos3 = -1;
    pos4 = -1;
   
    // If destination reached
    if (x1 == x2 && y1 == y2)
    {
        System.out.println("0");
    }
   
    // Iterate over the string
    else
    {
        for(int i = 0; i < n; i++)
        {
             
            // Move east
            if (x2 > x1)
            {
                 
                // Change x1 according
                // to direction E
                if (str.charAt(i) == 'E')
                {
                    x1 = x1 + 1;
                     
                    if (x1 == x2)
                    {
                        pos1 = i;
                    }
                }
            }
   
            // Move west
            if (x2 < x1)
            {
                 
                // Change x1 according
                // to direction W
                if (str.charAt(i) == 'W')
                {
                    x1 = x1 - 1;
                     
                    if (x1 == x2)
                    {
                        pos2 = i;
                    }
                }
            }
   
            // Move north
            if (y2 > y1)
            {
                 
                // Change y1 according
                // to direction N
                if (str.charAt(i) == 'N')
                {
                    y1 = y1 + 1;
                     
                    if (y1 == y2)
                    {
                        pos3 = i;
                    }
                }
            }
   
            // Move south
            if (y2 < y1)
            {
                 
                // Change y1 according
                // to direction S
                if (str.charAt(i) == 'S')
                {
                    y1 = y1 - 1;
                     
                    if (y1 == y2)
                    {
                        pos4 = i;
                    }
                }
            }
        }
        int z;
         
        // Store the max of all positions
        z = Math.max(pos1,
            Math.max(Math.max(pos2, pos3),
                              pos4));
                   
        // Print the minimum length of
        // string required
        if (x1 == x2 && y1 == y2)
        {
             System.out.println(z + 1); 
        }
   
        // Otherwise, it is impossible
        else
        {
             System.out.println("-1");
        }
    }
}
 
// Driver Code
public static void main (String[] args)
throws java.lang.Exception
{
     
    // Given string
    String str = "SESNW";
 
    // Given source and destination
    int x1 = 0, x2 = 1, y1 = 0, y2 = 1;
 
    // Function call
    minimum_length(x1, y1, x2, y2, str);
}
}
 
// This code is contributed by bikram2001jha

Python3

# Python3 program for the above approach
 
# Function to find the minimum length
# of string required to reach from
# source to destination
def minimum_length(x1, y1, x2, y2, str):
     
    # Size of the string
    n = len(str)
 
    # Stores the index of the four
    # directions E, W, N, S
    pos1 = -1
    pos2 = -1
    pos3 = -1
    pos4 = -1
 
    # If destination reached
    if (x1 == x2 and y1 == y2):
        print("0")
 
    # Iterate over the string
    else:
        for i in range(n):
 
            # Move east
            if (x2 > x1):
 
                # Change x1 according
                # to direction E
                if (str[i] == 'E'):
                    x1 = x1 + 1
 
                    if (x1 == x2):
                        pos1 = i
 
            # Move west
            if (x2 < x1):
 
                # Change x1 according
                # to direction W
                if (str[i] == 'W'):
                    x1 = x1 - 1
 
                    if (x1 == x2):
                        pos2 = i
 
            # Move north
            if (y2 > y1):
 
                # Change y1 according
                # to direction N
                if (str[i] == 'N'):
                    y1 = y1 + 1
 
                    if (y1 == y2):
                        pos3 = i
 
            # Move south
            if (y2 < y1):
 
                # Change y1 according
                # to direction S
                if (str[i] == 'S'):
                    y1 = y1 - 1
 
                    if (y1 == y2):
                        pos4 = i
 
        z = 0
 
        # Store the max of all positions
        z = max(pos1, max(max(pos2, pos3), pos4))
 
        # Print the minimum length of
        # string required
        if (x1 == x2 and y1 == y2):
            print(z + 1)
 
        # Otherwise, it is impossible
        else:
            print("-1")
 
# Driver Code
 
# Given string
str = "SESNW"
 
# Given source and destination
x1 = 0
x2 = 1
y1 = 0
y2 = 1
 
# Function call
minimum_length(x1, y1, x2, y2, str)
 
# This code is contributed by Amit Katiyar

C#

// C# program for the above approach
using System;
  
class GFG{
  
// Function to find the minimum length
// of string required to reach from
// source to destination
static void minimum_length(int x1, int y1,
                           int x2, int y2,
                           string str)
{
     
    // Size of the string
    int n = str.Length;
    
    // Stores the index of the four
    // directions E, W, N, S
    int pos1, pos2, pos3, pos4;
    pos1 = -1;
    pos2 = -1;
    pos3 = -1;
    pos4 = -1;
    
    // If destination reached
    if (x1 == x2 && y1 == y2)
    {
        Console.WriteLine("0");
    }
    
    // Iterate over the string
    else
    {
        for(int i = 0; i < n; i++)
        {
              
            // Move east
            if (x2 > x1)
            {
                  
                // Change x1 according
                // to direction E
                if (str[i] == 'E')
                {
                    x1 = x1 + 1;
                      
                    if (x1 == x2)
                    {
                        pos1 = i;
                    }
                }
            }
    
            // Move west
            if (x2 < x1)
            {
                  
                // Change x1 according
                // to direction W
                if (str[i] == 'W')
                {
                    x1 = x1 - 1;
                      
                    if (x1 == x2)
                    {
                        pos2 = i;
                    }
                }
            }
    
            // Move north
            if (y2 > y1)
            {
                  
                // Change y1 according
                // to direction N
                if (str[i] == 'N')
                {
                    y1 = y1 + 1;
                      
                    if (y1 == y2)
                    {
                        pos3 = i;
                    }
                }
            }
    
            // Move south
            if (y2 < y1)
            {
                  
                // Change y1 according
                // to direction S
                if (str[i] == 'S')
                {
                    y1 = y1 - 1;
                      
                    if (y1 == y2)
                    {
                        pos4 = i;
                    }
                }
            }
        }
        int z;
          
        // Store the max of all positions
        z = Math.Max(pos1,
            Math.Max(Math.Max(pos2, pos3),
                              pos4));
                    
        // Print the minimum length of
        // string required
        if (x1 == x2 && y1 == y2)
        {
             Console.WriteLine(z + 1); 
        }
    
        // Otherwise, it is impossible
        else
        {
             Console.WriteLine("-1");
        }
    }
}
  
// Driver Code
public static void Main ()
{
      
    // Given string
    string str = "SESNW";
  
    // Given source and destination
    int x1 = 0, x2 = 1, y1 = 0, y2 = 1;
  
    // Function call
    minimum_length(x1, y1, x2, y2, str);
}
}
 
// This code is contributed by sanjoy_62

Javascript

 
// Javascript program for the above approach
 
// Function to find the minimum length
// of string required to reach from
// source to destination
function minimum_length(x1, y1,
                    x2,  y2,
                     str)
{
 
    // Size of the string
    var n = str.length;
 
    // Stores the index of the four
    // directions E, W, N, S
    var pos1, pos2, pos3, pos4;
    pos1 = -1;
    pos2 = -1;
    pos3 = -1;
    pos4 = -1;
 
    // If destination reached
    if (x1 == x2 && y1 == y2) {
        document.write(0+"<br>");
    }
 
    // Iterate over the string
    else {
        for (var i = 0; i < n; i++) {
 
            // Move east
            if (x2 > x1) {
 
                // Change x1 according
                // to direction E
                if (str[i] == 'E') {
                    x1 = x1 + 1;
                    if (x1 == x2) {
                        pos1 = i;
                    }
                }
            }
 
            // Move west
            if (x2 < x1) {
 
                // Change x1 according
                // to direction W
                if (str[i] == 'W') {
                    x1 = x1 - 1;
                    if (x1 == x2) {
                        pos2 = i;
                    }
                }
            }
 
            // Move north
            if (y2 > y1) {
 
                // Change y1 according
                // to direction N
                if (str[i] == 'N')
                {
                    y1 = y1 + 1;
                    if (y1 == y2)
                    {
                        pos3 = i;
                    }
                }
            }
 
            // Move south
            if (y2 < y1) {
 
                // Change y1 according
                // to direction S
                if (str[i] == 'S') {
                    y1 = y1 - 1;
                    if (y1 == y2) {
                        pos4 = i;
                    }
                }
            }
        }
        var z;
         
        // Store the max of all positions
        z = Math.max(Math.max(Math.max(pos1, pos2),
                    pos3),
                pos4);
 
        // Print the minimum length of
        // string required
        if (x1 == x2 && y1 == y2) {
            document.write(z + 1 + "<br>" );
        }
 
        // Otherwise, it is impossible
        else {
            document.write("-1<br>");;
        }
    }
}
 
// Driver Code
 
// Given string
var str = "SESNW";
 
// Given source and destination
var x1 = 0, x2 = 1, y1 = 0, y2 = 1;
 
// Function Call
minimum_length(x1, y1, x2, y2, str);
 
// This code is contributed by rrrtnx.

输出：

4

时间复杂度： O(N)
辅助空间： O(1)