鉴于两个字符串str的长度为N和长度M的字，任务是从字符串str去除字符串词的所有出现。
例子：
Input: str = “asmGeeksasmasmForasmGeeks”, word = “asm”
Output: GeeksForGeeks
Explanation:
Removing “asm” from the string, str modifies str to GeeksForGeeks
Input: str = “Z-kmalgorithmkmiskmkmkmhelpfulkminkmsearching”, word = “km”
Output: Z-algorithmishelpfulinsearching
Explanation:
Removing “km” from the string, str modifies str to “Z-algorithmishelpfulinsearching”.
天真的方法：解决此问题的最简单方法是遍历字符串str的字符。对于每个索引，检查是否可以找到一个子字符串，该子字符串的起始索引等于当前索引，并且该子字符串等于字符串word 。如果发现为真，则删除子字符串。最后，打印字符串。
时间复杂度： O(N 2 )
辅助空间： O(1)
基于STL的方法：使用replace()方法从字符串str中删除所有出现的字符串单词。
时间复杂度： O(N 2 )
辅助空间： O(1)
高效方法：可以使用Z算法对上述方法进行优化。请按照以下步骤解决问题：
- 初始化一个字符串，例如res ，通过从给定字符串str中删除单词来存储该字符串。
- 初始化一个数组，例如Z [] ，以存储字符串的Z值。
- 使用Z算法查找给定字符串str中所有出现的字符串单词。
- 最后，遍历数组Z []并检查z [i + length(word)+1]是否等于length(word) 。如果发现是真的，则更新i + = length(word)– 1 。
- 否则，将当前字符附加到字符串res中。
下面是上述方法的实现：
C++
// C++ program for the above approach
#include
using namespace std;
// Function to fill the Z-array for str
void getZarr(string str, int Z[])
{
int n = str.length();
int k;
// L Stores start index of window
// which matches with prefix of str
int L = 0;
// R Stores end index of window
// which matches with prefix of str
int R = 0;
// Iterate over the characters of str
for (int i = 1; i < n; ++i) {
// If i is greater thn R
if (i > R) {
// Update L and R
L = R = i;
// If substring match with prefix
while (R < n && str[R - L] == str[R]) {
// Update R
R++;
}
// Update Z[i]
Z[i] = R - L;
// Update R
R--;
}
else {
// Update k
k = i - L;
// if Z[k] is less than
// remaining interval
if (Z[k] < R - i + 1) {
// Update Z[i]
Z[i] = Z[k];
}
else {
// Start from R and check manually
L = i;
while (R < n && str[R - L] == str[R]) {
// Update R
R++;
}
// Update Z[i]
Z[i] = R - L;
// Update R
R--;
}
}
}
}
// Function to remove all the occurrences
// of word from str
string goodStr(string str, string word)
{
// Create concatenated string "P$T"
string concat = word + "$" + str;
int l = concat.length();
// Store Z array of concat
int Z[l];
getZarr(concat, Z);
// Stores string, str by removing all
// the occurrences of word from str
string res;
// Stores length of word
int pSize = word.size();
// Traverse the array, Z[]
for (int i = 0; i < l; ++i) {
// if Z[i + pSize + 1] equal to
// length of word
if (i + pSize < l - 1 && Z[i + pSize + 1] == pSize) {
// Update i
i += pSize - 1;
}
else if (i < str.length()) {
res += str[i];
}
}
return res;
}
// Driver Code
int main()
{
string str
= "Z-kmalgorithmkmiskmkmkmhelpfulkminkmsearching";
string word = "km";
cout << goodStr(str, word);
return 0;
} Java
// Java program for the above approach
import java.util.*;
class GFG
{
// Function to fill the Z-array for str
static void getZarr(String str, int Z[])
{
int n = str.length();
int k;
// L Stores start index of window
// which matches with prefix of str
int L = 0;
// R Stores end index of window
// which matches with prefix of str
int R = 0;
// Iterate over the characters of str
for (int i = 1; i < n; ++i)
{
// If i is greater thn R
if (i > R)
{
// Update L and R
L = R = i;
// If subString match with prefix
while (R < n && str.charAt(R - L) ==
str.charAt(R))
{
// Update R
R++;
}
// Update Z[i]
Z[i] = R - L;
// Update R
R--;
}
else
{
// Update k
k = i - L;
// if Z[k] is less than
// remaining interval
if (Z[k] < R - i + 1)
{
// Update Z[i]
Z[i] = Z[k];
}
else
{
// Start from R and check manually
L = i;
while (R < n && str.charAt(R - L) ==
str.charAt(R))
{
// Update R
R++;
}
// Update Z[i]
Z[i] = R - L;
// Update R
R--;
}
}
}
}
// Function to remove all the occurrences
// of word from str
static String goodStr(String str, String word)
{
// Create concatenated String "P$T"
String concat = word + "$" + str;
int l = concat.length();
// Store Z array of concat
int []Z = new int[l];
getZarr(concat, Z);
// Stores String, str by removing all
// the occurrences of word from str
String res="";
// Stores length of word
int pSize = word.length();
// Traverse the array, Z[]
for (int i = 0; i < l; ++i) {
// if Z[i + pSize + 1] equal to
// length of word
if (i + pSize < l - 1 && Z[i + pSize + 1] == pSize) {
// Update i
i += pSize - 1;
}
else if (i < str.length()) {
res += str.charAt(i);
}
}
return res;
}
// Driver Code
public static void main(String[] args)
{
String str
= "Z-kmalgorithmkmiskmkmkmhelpfulkminkmsearching";
String word = "km";
System.out.print(goodStr(str, word));
}
}
// This code is contributed by 29AjayKumarPython3
# Python 3 program for the above approach
# Function to fill the Z-array for str
def getZarr(st, Z):
n = len(st)
k = 0
# L Stores start index of window
# which matches with prefix of str
L = 0
# R Stores end index of window
# which matches with prefix of str
R = 0
# Iterate over the characters of str
for i in range(1, n):
# If i is greater thn R
if (i > R):
# Update L and R
L = R = i
# If substring match with prefix
while (R < n and st[R - L] == st[R]):
# Update R
R += 1
# Update Z[i]
Z[i] = R - L
# Update R
R -= 1
else:
# Update k
k = i - L
# if Z[k] is less than
# remaining interval
if (Z[k] < R - i + 1):
# Update Z[i]
Z[i] = Z[k]
else:
# Start from R and check manually
L = i
while (R < n and st[R - L] == st[R]):
# Update R
R += 1
# Update Z[i]
Z[i] = R - L
# Update R
R -= 1
# Function to remove all the occurrences
# of word from str
def goodStr(st, word):
# Create concatenated string "P$T"
concat = word + "$" + st
l = len(concat)
# Store Z array of concat
Z = [0]*l
getZarr(concat, Z)
# Stores string, str by removing all
# the occurrences of word from str
res = ""
# Stores length of word
pSize = len(word)
# Traverse the array, Z[]
for i in range(l):
# if Z[i + pSize + 1] equal to
# length of word
if (i + pSize < l - 1 and Z[i + pSize + 1] == pSize):
# Update i
i += pSize - 1
elif (i < len(st)):
res += st[i]
return res
# Driver Code
if __name__ == "__main__":
st = "Z-kmalgorithmkmiskmkmkmhelpfulkminkmsearching"
word = "km"
print(goodStr(st, word))
# This code is contributed by chitranayal.C#
// C# program for the above approach
using System;
using System.Collections.Generic;
public class GFG
{
// Function to fill the Z-array for str
static void getZarr(string str, int[] Z)
{
int n = str.Length;
int k;
// L Stores start index of window
// which matches with prefix of str
int L = 0;
// R Stores end index of window
// which matches with prefix of str
int R = 0;
// Iterate over the characters of str
for (int i = 1; i < n; ++i)
{
// If i is greater thn R
if (i > R)
{
// Update L and R
L = R = i;
// If subString match with prefix
while (R < n && str[R - L] ==
str[R])
{
// Update R
R++;
}
// Update Z[i]
Z[i] = R - L;
// Update R
R--;
}
else
{
// Update k
k = i - L;
// if Z[k] is less than
// remaining interval
if (Z[k] < R - i + 1)
{
// Update Z[i]
Z[i] = Z[k];
}
else
{
// Start from R and check manually
L = i;
while (R < n && str[R - L] ==
str[R])
{
// Update R
R++;
}
// Update Z[i]
Z[i] = R - L;
// Update R
R--;
}
}
}
}
// Function to remove all the occurrences
// of word from str
static string goodStr(string str, string word)
{
// Create concatenated String "P$T"
string concat = word + "$" + str;
int l = concat.Length;
// Store Z array of concat
int []Z = new int[l];
getZarr(concat, Z);
// Stores String, str by removing all
// the occurrences of word from str
string res="";
// Stores length of word
int pSize = word.Length;
// Traverse the array, Z[]
for (int i = 0; i < l; ++i) {
// if Z[i + pSize + 1] equal to
// length of word
if (i + pSize < l - 1 && Z[i + pSize + 1] == pSize) {
// Update i
i += pSize - 1;
}
else if (i < str.Length) {
res += str[i];
}
}
return res;
}
// Driver Code
static public void Main()
{
string str
= "Z-kmalgorithmkmiskmkmkmhelpfulkminkmsearching";
string word = "km";
Console.WriteLine(goodStr(str, word));
}
}
// This code is contributed by sanjoy_62.输出：
Z-algorithmishelpfulinsearching时间复杂度： O(N + M)
辅助空间： O(N)