加权前缀搜索

鉴于 N 字符串和与每条字符串关联的权重。任务是找到具有给定前缀的字符串的最大重量。如果没有带给定前缀的字符串,则打印“-1”。 例如:

null
Input : s1 = "geeks", w1 = 15s2 = "geeksfor", w2 = 30s3 = "geeksforgeeks", w3 = 45prefix = geekOutput : 45All the string contain the given prefix, butmaximum weight of string is 45 among all.

方法1:(暴力)

检查给定前缀的所有字符串,如果字符串包含前缀,请将其权重与迄今为止的最大值进行比较。 以下是上述理念的实施:

C++

// C++ program to find the maximum weight with given prefix.
// Brute Force based C++ program to find the
// string with maximum weight and given prefix.
#include<bits/stdc++.h>
#define MAX 1000
using namespace std;
// Return the maximum weight of string having
// given prefix.
int maxWeight( char str[MAX][MAX], int weight[],
int n, char prefix[])
{
int ans = -1;
bool check;
// Traversing all strings
for ( int i = 0; i < n; i++)
{
check = true ;
// Checking if string contain given prefix.
for ( int j=0, k=0; j < strlen (str[i]) &&
k < strlen (prefix); j++, k++)
{
if (str[i][j] != prefix[k])
{
check = false ;
break ;
}
}
// If contain prefix then finding
// the maximum value.
if (check)
ans = max(ans, weight[i]);
}
return ans;
}
// Driven program
int main()
{
int n = 3;
char str[3][MAX] = { "geeks" , "geeksfor" , "geeksforgeeks" };
int weight[] = {15, 30, 45};
char prefix[] = "geek" ;
cout << maxWeight(str, weight, n, prefix) << endl;
return 0;
}


JAVA

// Java program to find the maximum
// weight with given prefix.
class GFG {
static final int MAX = 1000 ;
// Return the maximum weight of string having
// given prefix.
static int maxWeight(String str[], int weight[],
int n, String prefix)
{
int ans = - 1 ;
boolean check;
// Traversing all strings
for ( int i = 0 ; i < n; i++)
{
check = true ;
// Checking if string contain given prefix.
for ( int j= 0 , k= 0 ; j < str[i].length() &&
k < prefix.length(); j++, k++)
{
if (str[i].charAt(j) != prefix.charAt(k))
{
check = false ;
break ;
}
}
// If contain prefix then finding
// the maximum value.
if (check)
ans = Math.max(ans, weight[i]);
}
return ans;
}
// Driven program
public static void main(String args[])
{
int n = 3 ;
String str[] = { "geeks" , "geeksfor" , "geeksforgeeks" };
int weight[] = { 15 , 30 , 45 };
String prefix = "geek" ;
System.out.println(maxWeight(str, weight, n, prefix));
}
}
//This code is contributed by Sumit Ghosh


C#

// C# program to find the maximum weight
// with given prefix.
using System;
class GFG
{
// Return the maximum weight of
// string having given prefix.
static int maxWeight( string []str, int []weight,
int n, string prefix)
{
int ans = -1;
bool check;
// Traversing all strings
for ( int i = 0; i < n; i++)
{
check = true ;
// Checking if string contain given prefix.
for ( int j=0, k=0; j < str[i].Length &&
k < prefix.Length; j++, k++)
{
if (str[i][j] != prefix[k])
{
check = false ;
break ;
}
}
// If contain prefix then finding
// the maximum value.
if (check)
ans = Math.Max(ans, weight[i]);
}
return ans;
}
// Driver Code
public static void Main()
{
int n = 3;
String []str = { "geeks" , "geeksfor" ,
"geeksforgeeks" };
int []weight = {15, 30, 45};
String prefix = "geek" ;
Console.WriteLine(maxWeight(str, weight,
n, prefix));
}
}
// This code is contributed by vt_m.


Javascript

<script>
// Javascript program to find the maximum weight with given prefix.
// Return the maximum weight of
// string having given prefix.
function maxWeight(str, weight, n, prefix)
{
let ans = -1;
let check;
// Traversing all strings
for (let i = 0; i < n; i++)
{
check = true ;
// Checking if string contain given prefix.
for (let j=0, k=0; j < str[i].length &&
k < prefix.length; j++, k++)
{
if (str[i][j] != prefix[k])
{
check = false ;
break ;
}
}
// If contain prefix then finding
// the maximum value.
if (check)
ans = Math.max(ans, weight[i]);
}
return ans;
}
let n = 3;
let str = [ "geeks" , "geeksfor" , "geeksforgeeks" ];
let weight = [15, 30, 45];
let prefix = "geek" ;
document.write(maxWeight(str, weight,
n, prefix));
</script>


输出:

45

方法2(高效):

其想法是创建并维护一个Trie。与存储字符的普通Trie不同,存储一个数字,这是其前缀的最大值。当我们再次遇到前缀时,用现有和新前缀的最大值更新该值。 现在,搜索前缀的最大值,从根开始遍历字符,如果其中一个字符缺失,返回-1,否则返回存储在根中的数字。 以下是上述理念的实施情况:

C++

// C++ program to find the maximum weight
// with given prefix.
#include<bits/stdc++.h>
#define MAX 1000
using namespace std;
// Structure of a trie node
struct trieNode
{
// Pointer its children.
struct trieNode *children[26];
// To store weight of string.
int weight;
};
// Create and return a Trie node
struct trieNode* getNode()
{
struct trieNode *node = new trieNode;
node -> weight = INT_MIN;
for ( int i = 0; i < 26; i++)
node -> children[i] = NULL;
}
// Inserting the node in the Trie.
struct trieNode* insert( char str[], int wt, int idx,
struct trieNode* root)
{
int cur = str[idx] - 'a' ;
if (!root -> children[cur])
root -> children[cur] = getNode();
// Assigning the maximum weight
root->children[cur]->weight =
max(root->children[cur]->weight, wt);
if (idx + 1 != strlen (str))
root -> children[cur] =
insert(str, wt, idx + 1, root -> children[cur]);
return root;
}
// Search and return the maximum weight.
int searchMaximum( char prefix[], struct trieNode *root)
{
int idx = 0, n = strlen (prefix), ans = -1;
// Searching the prefix in TRie.
while (idx < n)
{
int cur = prefix[idx] - 'a' ;
// If prefix not found return -1.
if (!root->children[cur])
return -1;
ans = root->children[cur]->weight;
root = root->children[cur];
++idx;
}
return ans;
}
// Return the maximum weight of string having given prefix.
int maxWeight( char str[MAX][MAX], int weight[], int n,
char prefix[])
{
struct trieNode* root = getNode();
// Inserting all string in the Trie.
for ( int i = 0; i < n; i++)
root = insert(str[i], weight[i], 0, root);
return searchMaximum(prefix, root);
}
// Driven Program
int main()
{
int n = 3;
char str[3][MAX] = { "geeks" , "geeksfor" , "geeksforgeeks" };
int weight[] = {15, 30, 45};
char prefix[] = "geek" ;
cout << maxWeight(str, weight, n, prefix) << endl;
return 0;
}


JAVA

// Java program to find the maximum weight
// with given prefix.
public class GFG{
static final int MAX = 1000 ;
// Structure of a trie node
static class TrieNode
{
// children
TrieNode[] children = new TrieNode[ 26 ];
// To store weight of string.
int weight;
// constructor
public TrieNode() {
weight = Integer.MIN_VALUE;
for ( int i = 0 ; i < 26 ; i++)
children[i] = null ;
}
}
//static TrieNode root;
// Inserting the node in the Trie.
static TrieNode insert(String str, int wt, int idx, TrieNode root)
{
int cur = str.charAt(idx) - 'a' ;
if (root.children[cur] == null )
root.children[cur] = new TrieNode();
// Assigning the maximum weight
root.children[cur].weight =
Math.max(root.children[cur].weight, wt);
if (idx + 1 != str.length())
root.children[cur] =
insert(str, wt, idx + 1 , root.children[cur]);
return root;
}
// Search and return the maximum weight.
static int searchMaximum(String prefix, TrieNode root)
{
int idx = 0 , ans = - 1 ;
int n = prefix.length();
// Searching the prefix in TRie.
while (idx < n)
{
int cur = prefix.charAt(idx) - 'a' ;
// If prefix not found return -1.
if (root.children[cur] == null )
return - 1 ;
ans = root.children[cur].weight;
root = root.children[cur];
++idx;
}
return ans;
}
// Return the maximum weight of string having given prefix.
static int maxWeight(String str[], int weight[], int n,
String prefix)
{
TrieNode root = new TrieNode();
// Inserting all string in the Trie.
for ( int i = 0 ; i < n; i++)
root = insert(str[i], weight[i], 0 , root);
return searchMaximum(prefix, root);
}
// Driven Program
public static void main(String args[])
{
int n = 3 ;
String str[] = { "geeks" , "geeksfor" , "geeksforgeeks" };
int weight[] = { 15 , 30 , 45 };
String prefix = "geek" ;
System.out.println(maxWeight(str, weight, n, prefix));
}
}
//This code is contributed by Sumit Ghosh


45

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