由无限连接给定数组形成的数组中给定范围内的元素总和
给定一个由N个正整数和两个正整数L和R组成的数组arr[] (基于 1 的索引),如果给定数组arr[] ,任务是在[L, R]范围内找到数组元素的总和无限次连接到自身。
例子:
Input: arr[] = {1, 2, 3}, L = 2, R = 8
Output: 14
Explanation:
The array, arr[] after concatenation is {1, 2, 3, 1, 2, 3, 1, 2, …} and the sum of elements from index 2 to 8 is 2 + 3 + 1 + 2 + 3 + 1 + 2 = 14.
Input: arr[] = {5, 2, 6, 9}, L = 10, R = 13
Output: 22
朴素方法:解决给定问题的最简单方法是使用变量i在范围[L, R]上进行迭代,并将arr[i % N]的值添加到每个索引的总和中。完成迭代后,将总和的值打印为结果总和。
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 sum of elements
// in a given range of an infinite array
void rangeSum(int arr[], int N, int L, int R)
{
// Stores the sum of array elements
// from L to R
int sum = 0;
// Traverse from L to R
for (int i = L - 1; i < R; i++) {
sum += arr[i % N];
}
// Print the resultant sum
cout << sum;
}
// Driver Code
int main()
{
int arr[] = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = sizeof(arr) / sizeof(arr[0]);
rangeSum(arr, N, L, R);
return 0;
}
Java
// Java program for the above approach
import java.io.*;
class GFG
{
// Function to find the sum of elements
// in a given range of an infinite array
static void rangeSum(int arr[], int N, int L, int R)
{
// Stores the sum of array elements
// from L to R
int sum = 0;
// Traverse from L to R
for (int i = L - 1; i < R; i++) {
sum += arr[i % N];
}
// Print the resultant sum
System.out.println(sum);
}
// Driver Code
public static void main(String[] args)
{
int arr[] = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = arr.length;
rangeSum(arr, N, L, R);
}
}
// This code is contributed by Potta Lokesh
Python3
# Python 3 program for the above approach
# Function to find the sum of elements
# in a given range of an infinite array
def rangeSum(arr, N, L, R):
# Stores the sum of array elements
# from L to R
sum = 0
# Traverse from L to R
for i in range(L - 1,R,1):
sum += arr[i % N]
# Print the resultant sum
print(sum)
# Driver Code
if __name__ == '__main__':
arr = [5, 2, 6, 9 ]
L = 10
R = 13
N = len(arr)
rangeSum(arr, N, L, R)
# This code is contributed by divyeshrabadiya07
C#
// C# program for the above approach
using System;
class GFG {
// Function to find the sum of elements
// in a given range of an infinite array
static void rangeSum(int[] arr, int N, int L, int R)
{
// Stores the sum of array elements
// from L to R
int sum = 0;
// Traverse from L to R
for (int i = L - 1; i < R; i++) {
sum += arr[i % N];
}
// Print the resultant sum
Console.Write(sum);
}
// Driver Code
public static void Main(string[] args)
{
int[] arr = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = arr.Length;
rangeSum(arr, N, L, R);
}
}
// This code is contributed by ukasp.
Javascript
C++
// C++ program for the above approach
#include
using namespace std;
// Function to find the sum of elements
// in a given range of an infinite array
void rangeSum(int arr[], int N, int L,
int R)
{
// Stores the prefix sum
int prefix[N + 1];
prefix[0] = 0;
// Calculate the prefix sum
for (int i = 1; i <= N; i++) {
prefix[i] = prefix[i - 1]
+ arr[i - 1];
}
// Stores the sum of elements
// from 1 to L-1
int leftsum
= ((L - 1) / N) * prefix[N]
+ prefix[(L - 1) % N];
// Stores the sum of elements
// from 1 to R
int rightsum = (R / N) * prefix[N]
+ prefix[R % N];
// Print the resultant sum
cout << rightsum - leftsum;
}
// Driver Code
int main()
{
int arr[] = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = sizeof(arr) / sizeof(arr[0]);
rangeSum(arr, N, L, R);
return 0;
}
Java
// Java program for the above approach
import java.io.*;
class GFG{
// Function to find the sum of elements
// in a given range of an infinite array
static void rangeSum(int arr[], int N, int L, int R)
{
// Stores the prefix sum
int prefix[] = new int[N+1];
prefix[0] = 0;
// Calculate the prefix sum
for (int i = 1; i <= N; i++) {
prefix[i] = prefix[i - 1]
+ arr[i - 1];
}
// Stores the sum of elements
// from 1 to L-1
int leftsum
= ((L - 1) / N) * prefix[N]
+ prefix[(L - 1) % N];
// Stores the sum of elements
// from 1 to R
int rightsum = (R / N) * prefix[N]
+ prefix[R % N];
// Print the resultant sum
System.out.print( rightsum - leftsum);
}
// Driver Code
public static void main (String[] args)
{
int arr[] = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = arr.length;
rangeSum(arr, N, L, R);
}
}
// This code is contributed by shivanisinghss2110
Python3
# Python 3 program for the above approach
# Function to find the sum of elements
# in a given range of an infinite array
def rangeSum(arr, N, L, R):
# Stores the prefix sum
prefix = [0 for i in range(N + 1)]
prefix[0] = 0
# Calculate the prefix sum
for i in range(1,N+1,1):
prefix[i] = prefix[i - 1] + arr[i - 1]
# Stores the sum of elements
# from 1 to L-1
leftsum = ((L - 1) // N) * prefix[N] + prefix[(L - 1) % N]
# Stores the sum of elements
# from 1 to R
rightsum = (R // N) * prefix[N] + prefix[R % N]
# Print the resultant sum
print(rightsum - leftsum)
# Driver Code
if __name__ == '__main__':
arr = [5, 2, 6, 9]
L = 10
R = 13
N = len(arr)
rangeSum(arr, N, L, R)
# This code is contributed by SURENDRA_GANGWAR.
C#
// C# program for the above approach
using System;
class GFG{
// Function to find the sum of elements
// in a given range of an infinite array
static void rangeSum(int []arr, int N, int L, int R)
{
// Stores the prefix sum
int []prefix = new int[N+1];
prefix[0] = 0;
// Calculate the prefix sum
for (int i = 1; i <= N; i++) {
prefix[i] = prefix[i - 1]
+ arr[i - 1];
}
// Stores the sum of elements
// from 1 to L-1
int leftsum
= ((L - 1) / N) * prefix[N]
+ prefix[(L - 1) % N];
// Stores the sum of elements
// from 1 to R
int rightsum = (R / N) * prefix[N]
+ prefix[R % N];
// Print the resultant sum
Console.Write( rightsum - leftsum);
}
// Driver Code
public static void Main (String[] args)
{
int []arr = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = arr.Length;
rangeSum(arr, N, L, R);
}
}
// This code is contributed by shivanisinghss2110
Javascript
输出:
22
时间复杂度: O(R – L)
辅助空间: O(1)
高效方法:上述方法也可以通过使用前缀和进行优化。请按照以下步骤解决问题:
- 初始化一个数组,比如大小为(N + 1)的prefix[] ,所有元素都为0s 。
- 使用变量i遍历数组arr[]并将prefix[i]更新为prefix[i – 1]和arr[i – 1]的总和。
- 现在, [L, R]范围内的元素总和由下式给出:
the sum of elements in the range [1, R] – sum of elements in the range [1, L – 1].
- 初始化一个变量,例如leftSum为((L – 1)/N)*prefix[N] + prefix[(L – 1)%N]以存储范围[1, L-1]中元素的总和。
- 类似地,将另一个变量rightSum初始化为(R/N)*prefix[N] + prefix[R%N]以存储[1, R]范围内元素的总和。
- 完成上述步骤后,将(rightSum – leftSum)的值打印为给定范围[L, R]内元素的总和。
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 sum of elements
// in a given range of an infinite array
void rangeSum(int arr[], int N, int L,
int R)
{
// Stores the prefix sum
int prefix[N + 1];
prefix[0] = 0;
// Calculate the prefix sum
for (int i = 1; i <= N; i++) {
prefix[i] = prefix[i - 1]
+ arr[i - 1];
}
// Stores the sum of elements
// from 1 to L-1
int leftsum
= ((L - 1) / N) * prefix[N]
+ prefix[(L - 1) % N];
// Stores the sum of elements
// from 1 to R
int rightsum = (R / N) * prefix[N]
+ prefix[R % N];
// Print the resultant sum
cout << rightsum - leftsum;
}
// Driver Code
int main()
{
int arr[] = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = sizeof(arr) / sizeof(arr[0]);
rangeSum(arr, N, L, R);
return 0;
}
Java
// Java program for the above approach
import java.io.*;
class GFG{
// Function to find the sum of elements
// in a given range of an infinite array
static void rangeSum(int arr[], int N, int L, int R)
{
// Stores the prefix sum
int prefix[] = new int[N+1];
prefix[0] = 0;
// Calculate the prefix sum
for (int i = 1; i <= N; i++) {
prefix[i] = prefix[i - 1]
+ arr[i - 1];
}
// Stores the sum of elements
// from 1 to L-1
int leftsum
= ((L - 1) / N) * prefix[N]
+ prefix[(L - 1) % N];
// Stores the sum of elements
// from 1 to R
int rightsum = (R / N) * prefix[N]
+ prefix[R % N];
// Print the resultant sum
System.out.print( rightsum - leftsum);
}
// Driver Code
public static void main (String[] args)
{
int arr[] = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = arr.length;
rangeSum(arr, N, L, R);
}
}
// This code is contributed by shivanisinghss2110
Python3
# Python 3 program for the above approach
# Function to find the sum of elements
# in a given range of an infinite array
def rangeSum(arr, N, L, R):
# Stores the prefix sum
prefix = [0 for i in range(N + 1)]
prefix[0] = 0
# Calculate the prefix sum
for i in range(1,N+1,1):
prefix[i] = prefix[i - 1] + arr[i - 1]
# Stores the sum of elements
# from 1 to L-1
leftsum = ((L - 1) // N) * prefix[N] + prefix[(L - 1) % N]
# Stores the sum of elements
# from 1 to R
rightsum = (R // N) * prefix[N] + prefix[R % N]
# Print the resultant sum
print(rightsum - leftsum)
# Driver Code
if __name__ == '__main__':
arr = [5, 2, 6, 9]
L = 10
R = 13
N = len(arr)
rangeSum(arr, N, L, R)
# This code is contributed by SURENDRA_GANGWAR.
C#
// C# program for the above approach
using System;
class GFG{
// Function to find the sum of elements
// in a given range of an infinite array
static void rangeSum(int []arr, int N, int L, int R)
{
// Stores the prefix sum
int []prefix = new int[N+1];
prefix[0] = 0;
// Calculate the prefix sum
for (int i = 1; i <= N; i++) {
prefix[i] = prefix[i - 1]
+ arr[i - 1];
}
// Stores the sum of elements
// from 1 to L-1
int leftsum
= ((L - 1) / N) * prefix[N]
+ prefix[(L - 1) % N];
// Stores the sum of elements
// from 1 to R
int rightsum = (R / N) * prefix[N]
+ prefix[R % N];
// Print the resultant sum
Console.Write( rightsum - leftsum);
}
// Driver Code
public static void Main (String[] args)
{
int []arr = { 5, 2, 6, 9 };
int L = 10, R = 13;
int N = arr.Length;
rangeSum(arr, N, L, R);
}
}
// This code is contributed by shivanisinghss2110
Javascript
输出:
22
时间复杂度: O(N)
辅助空间: O(N)