求给定整数序列中 L 到 R 范围内的和
原文:https://www . geesforgeks . org/find-sum-in-range-l-to-r-in-给定整数序列/
给定一个整数的数组 arr[] 和一个形式为: 的序列
【2，3，0，1，6，7，4，5，…】。
还给出了两个整数 L 和 R ，这样
。任务是找出从 L 到 r 的给定范围内所有数字的和
示例:
Input : L = 0, R = 5
Output : 19
Explanation :
The arr[] is {2, 3, 0, 1, 6, 7}.
sum = arr[0] + arr[1] + arr[2] + arr[3] + arr[4] + arr[5]
sum = 2 + 3 + 0 + 1 + 6 + 7
Hence, the sum is 19.
Input : L = 2, R = 5
Output : 14
Explanation :
The arr[] is {0, 1, 6, 7}.
sum = arr[2] + arr[3] + arr[4] + arr[5]
sum = 0 + 1 + 6 + 7
Hence, the sum is 14.
方法: 要解决上面提到的问题，我们首先要观察数组的顺序，了解它是如何生成的。给定的数组是由一系列整数生成的，这些整数是[ 0，1，2，3，4，5，6，… ]。最初我们在前两个整数上加 2，然后我们从后两个整数上减去 2，如此继续。所以我们新形成的数组看起来像[ 0+2，1+2，2-2，3-2，4+2，5+2，6-2，7-2，… ]。因此，我们生成这个新的整数序列，并将其存储在数组中。最后，计算范围从 L 到 R 的指数之和并返回。 以下是上述方法的实施:
C++
// C++ program to find the
// sum in given range L to R
#include <bits/stdc++.h>
using namespace std;
// Function to find the sum
// within the given range
int findSum(int L, int R)
{
vector<int> arr;
// generating array from given sequence
int i = 0;
int x = 2;
while (i <= R) {
arr.push_back(i + x);
if (i + 1 <= R)
arr.push_back(i + 1 + x);
x *= -1;
i += 2;
}
// calculate the desired sum
int sum = 0;
for (int i = L; i <= R; ++i)
sum += arr[i];
// return the sum
return sum;
}
// Driven code
int main()
{
// initialise the range
int L = 0, R = 5;
cout << findSum(L, R);
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to find the
// sum in given range L to R
import java.util.*;
class GFG{
// Function to find the sum
// within the given range
public static int findSum(int L, int R)
{
ArrayList<Integer> arr = new ArrayList<>();
// Generating array from given sequence
int i = 0;
int x = 2;
while (i <= R)
{
arr.add(i + x);
if (i + 1 <= R)
arr.add(i + 1 + x);
x *= -1;
i += 2;
}
// Calculate the desired sum
int sum = 0;
for(i = L; i <= R; ++i)
sum += arr.get(i);
// return the sum
return sum;
}
// Driver code
public static void main(String[] args)
{
// Initialise the range
int L = 0, R = 5;
System.out.println(findSum(L, R));
}
}
// This code is contributed by jrishabh99
Python 3
# Python3 program to find the
# sum in given range L to R
# Function to find the sum
# within the given range
def findSum(L, R) :
arr = []
# generating array from given sequence
i = 0
x = 2
k = 0
while (i <= R) :
arr.insert(k, i + x)
k += 1
if (i + 1 <= R) :
arr.insert(k, i + 1 + x)
k += 1
x *= -1
i += 2
# calculate the desired sum
sum = 0
for i in range(L, R + 1) :
sum += arr[i]
# return the sum
return sum
# Driver code
# initialise the range
L = 0
R = 5
print(findSum(L, R))
# This code is contributed by Sanjit_Prasad
C
// C# program to find the
// sum in given range L to R
using System;
using System.Collections;
class GFG{
// Function to find the sum
// within the given range
public static int findSum(int L, int R)
{
ArrayList arr = new ArrayList();
// Generating array from given sequence
int i = 0;
int x = 2;
while (i <= R)
{
arr.Add(i + x);
if (i + 1 <= R)
arr.Add(i + 1 + x);
x *= -1;
i += 2;
}
// Calculate the desired sum
int sum = 0;
for(i = L; i <= R; ++i)
sum += (int)arr[i];
// return the sum
return sum;
}
// Driver code
public static void Main(string[] args)
{
// Initialise the range
int L = 0, R = 5;
Console.Write(findSum(L, R));
}
}
// This code is contributed by rutvik_56
java 描述语言
<script>
//Javascript program to find the
// sum in given range L to R
// Function to find the sum
// within the given range
function findSum( L, R)
{
var arr=[];
// generating array from given sequence
var i = 0;
var x = 2;
while (i <= R) {
arr.push(i + x);
if (i + 1 <= R)
arr.push(i + 1 + x);
x *= -1;
i += 2;
}
// calculate the desired sum
var sum = 0;
for (var i = L; i <= R; ++i)
sum += arr[i];
// return the sum
return sum;
}
var L = 0, R = 5;
document.write( findSum(L, R));
//This code is contributed by SoumikMondal
</script>
Output:
19
时间复杂度: O(N)
辅助空间: O(N)
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