给定N个元素的数组arr [] ,任务是更新所有数组元素,以使元素arr [i]更新为arr [i] = arr [i] – X其中X = arr [i + 1] + arr [i + 2] +…+ arr [N – 1] ,最后打印更新后的数组之和。
例子:
Input: arr[] = {40, 25, 12, 10}
Output: 8
The updated array will be {-7, 3, 2, 10}.
-7 + 3 + 2 + 10 = 8
Input: arr[] = {50, 30, 10, 2, 0}
Output: 36
方法:对于i的每个可能值,一个简单的解决方案是更新arr [i] = arr [i] – sum(arr [i + 1…N-1])。
C++
// C++ implementation of the approach
#include
using namespace std;
// Utility function to return
// the sum of the array
int sumArr(int arr[], int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
int sumModArr(int arr[], int n)
{
for (int i = 0; i < n - 1; i++) {
// Find the sum of the subarray
// arr[i+1...n-1]
int subSum = 0;
for (int j = i + 1; j < n; j++) {
subSum += arr[j];
}
// Subtract the subarray sum
arr[i] -= subSum;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
int main()
{
int arr[] = { 40, 25, 12, 10 };
int n = sizeof(arr) / sizeof(arr[0]);
cout << sumModArr(arr, n);
return 0;
}
Java
// Java implementation of the approach
import java.util.*;
class GFG
{
// Utility function to return
// the sum of the array
static int sumArr(int arr[], int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
static int sumModArr(int arr[], int n)
{
for (int i = 0; i < n - 1; i++)
{
// Find the sum of the subarray
// arr[i+1...n-1]
int subSum = 0;
for (int j = i + 1; j < n; j++)
{
subSum += arr[j];
}
// Subtract the subarray sum
arr[i] -= subSum;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
public static void main(String []args)
{
int arr[] = { 40, 25, 12, 10 };
int n = arr.length;
System.out.println(sumModArr(arr, n));
}
}
// This code is contributed by Rajput-Ji
Python3
# Python3 implementation of the approach
# Utility function to return
# the sum of the array
def sumArr(arr, n):
sum = 0
for i in range(n):
sum += arr[i]
return sum
# Function to return the sum
# of the modified array
def sumModArr(arr, n):
for i in range(n - 1):
# Find the sum of the subarray
# arr[i+1...n-1]
subSum = 0
for j in range(i + 1, n):
subSum += arr[j]
# Subtract the subarray sum
arr[i] -= subSum
# Return the sum of
# the modified array
return sumArr(arr, n)
# Driver code
arr = [40, 25, 12, 10]
n = len(arr)
print(sumModArr(arr, n))
# This code is contributed by Mohit Kumar
C#
// C# implementation of the approach
using System;
class GFG
{
// Utility function to return
// the sum of the array
static int sumArr(int []arr, int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
static int sumModArr(int []arr, int n)
{
for (int i = 0; i < n - 1; i++)
{
// Find the sum of the subarray
// arr[i+1...n-1]
int subSum = 0;
for (int j = i + 1; j < n; j++)
{
subSum += arr[j];
}
// Subtract the subarray sum
arr[i] -= subSum;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
public static void Main()
{
int []arr = { 40, 25, 12, 10 };
int n = arr.Length;
Console.WriteLine(sumModArr(arr, n));
}
}
// This code is contributed by AnkitRai01
C++
// C++ implementation of the approach
#include
using namespace std;
// Utility function to return
// the sum of the array
int sumArr(int arr[], int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
int sumModArr(int arr[], int n)
{
int subSum = arr[n - 1];
for (int i = n - 2; i >= 0; i--) {
int curr = arr[i];
// Subtract the subarray sum
arr[i] -= subSum;
// Sum of subarray arr[i...n-1]
subSum += curr;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
int main()
{
int arr[] = { 40, 25, 12, 10 };
int n = sizeof(arr) / sizeof(arr[0]);
cout << sumModArr(arr, n);
return 0;
}
Java
// Java implementation of the approach
class GFG
{
// Utility function to return
// the sum of the array
static int sumArr(int arr[], int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
static int sumModArr(int arr[], int n)
{
int subSum = arr[n - 1];
for (int i = n - 2; i >= 0; i--)
{
int curr = arr[i];
// Subtract the subarray sum
arr[i] -= subSum;
// Sum of subarray arr[i...n-1]
subSum += curr;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
public static void main (String[] args)
{
int []arr = { 40, 25, 12, 10 };
int n = arr.length;
System.out.println(sumModArr(arr, n));
}
}
// This code is contributed by kanugargng
Python3
# Python3 implementation of the approach
# Utility function to return
# the sum of the array
def sumArr(arr, n):
sum = 0;
for i in range(n):
sum += arr[i];
return sum;
# Function to return the sum
# of the modified array
def sumModArr(arr, n):
subSum = arr[n - 1];
for i in range(n - 2, -1, -1):
curr = arr[i];
# Subtract the subarray sum
arr[i] -= subSum;
# Sum of subarray arr[i...n-1]
subSum += curr;
# Return the sum of
# the modified array
return sumArr(arr, n);
# Driver code
arr = [40, 25, 12, 10 ];
n = len(arr);
print(sumModArr(arr, n));
# This code is contributed by 29AjayKumar
C#
// C# implementation of the approach
using System;
class GFG
{
// Utility function to return
// the sum of the array
static int sumArr(int []arr, int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
static int sumModArr(int []arr, int n)
{
int subSum = arr[n - 1];
for (int i = n - 2; i >= 0; i--)
{
int curr = arr[i];
// Subtract the subarray sum
arr[i] -= subSum;
// Sum of subarray arr[i...n-1]
subSum += curr;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
public static void Main (String[] args)
{
int []arr = { 40, 25, 12, 10 };
int n = arr.Length;
Console.WriteLine(sumModArr(arr, n));
}
}
// This code is contributed by 29AjayKumar
输出:
8
时间复杂度: O(N 2 )
高效的方法:一种有效的解决方案是从末尾遍历数组,以便直到现在为止子数组的总和,即sum(arr [i + 1…n-1])可用于计算当前子数组arr [ i…n-1]即sum(arr [i…n-1])= arr [i] + sum(arr [i + 1…n-1]) 。
下面是上述方法的实现:
C++
// C++ implementation of the approach
#include
using namespace std;
// Utility function to return
// the sum of the array
int sumArr(int arr[], int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
int sumModArr(int arr[], int n)
{
int subSum = arr[n - 1];
for (int i = n - 2; i >= 0; i--) {
int curr = arr[i];
// Subtract the subarray sum
arr[i] -= subSum;
// Sum of subarray arr[i...n-1]
subSum += curr;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
int main()
{
int arr[] = { 40, 25, 12, 10 };
int n = sizeof(arr) / sizeof(arr[0]);
cout << sumModArr(arr, n);
return 0;
}
Java
// Java implementation of the approach
class GFG
{
// Utility function to return
// the sum of the array
static int sumArr(int arr[], int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
static int sumModArr(int arr[], int n)
{
int subSum = arr[n - 1];
for (int i = n - 2; i >= 0; i--)
{
int curr = arr[i];
// Subtract the subarray sum
arr[i] -= subSum;
// Sum of subarray arr[i...n-1]
subSum += curr;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
public static void main (String[] args)
{
int []arr = { 40, 25, 12, 10 };
int n = arr.length;
System.out.println(sumModArr(arr, n));
}
}
// This code is contributed by kanugargng
Python3
# Python3 implementation of the approach
# Utility function to return
# the sum of the array
def sumArr(arr, n):
sum = 0;
for i in range(n):
sum += arr[i];
return sum;
# Function to return the sum
# of the modified array
def sumModArr(arr, n):
subSum = arr[n - 1];
for i in range(n - 2, -1, -1):
curr = arr[i];
# Subtract the subarray sum
arr[i] -= subSum;
# Sum of subarray arr[i...n-1]
subSum += curr;
# Return the sum of
# the modified array
return sumArr(arr, n);
# Driver code
arr = [40, 25, 12, 10 ];
n = len(arr);
print(sumModArr(arr, n));
# This code is contributed by 29AjayKumar
C#
// C# implementation of the approach
using System;
class GFG
{
// Utility function to return
// the sum of the array
static int sumArr(int []arr, int n)
{
int sum = 0;
for (int i = 0; i < n; i++)
sum += arr[i];
return sum;
}
// Function to return the sum
// of the modified array
static int sumModArr(int []arr, int n)
{
int subSum = arr[n - 1];
for (int i = n - 2; i >= 0; i--)
{
int curr = arr[i];
// Subtract the subarray sum
arr[i] -= subSum;
// Sum of subarray arr[i...n-1]
subSum += curr;
}
// Return the sum of
// the modified array
return sumArr(arr, n);
}
// Driver code
public static void Main (String[] args)
{
int []arr = { 40, 25, 12, 10 };
int n = arr.Length;
Console.WriteLine(sumModArr(arr, n));
}
}
// This code is contributed by 29AjayKumar
输出:
8
时间复杂度: O(N)