PROJECTENGRAM

02 - SIMPLE ARRAY SUM

Tags: #◇Computer Science #◇CSALGCM #◇Algorithms and Complexity #◇HackerRank #◇Fool Arcana #◇Arrays

Simple Array Sum

◇Problem Description

Given an array of integers, find the sum of its elements.

Input Format:

  • First line: integer n (size of the array)
  • Second line: n space-separated integers

Output Format:

  • A single integer representing the sum of all elements

Constraints: 0<n≤10000 < n \leq 1000; each element 0<a[i]≤10000 < a[i] \leq 1000

Sample:

InputOutput
6
1 2 3 4 10 11		31

◇Approach & Intuition

This is a basic linear scan aggregation problem. You read each element once and accumulate it into a running sum. This is the most fundamental pattern in array processing and underpins more complex algorithms like prefix sums and sliding windows.

Strategy:

  1. Initialize a sum variable to 0.
  2. Loop over every element x in the array.
  3. Add x to sum.
  4. Return sum.

[!note] Why use a range-based for loop?
for (int x : ar) is idiomatic modern C++ and avoids index-out-of-bounds errors. It is equivalent to iterating i = 0 to ar.size() - 1 but cleaner and harder to get wrong.

◇Complexity Analysis

Complexity
TimeO(n)O(n) — every element is visited exactly once.
SpaceO(1)O(1) — only the accumulator sum is stored beyond the input array itself.

◇Original Stub (HackerRank Template)

『』
CPP
#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * Complete the 'simpleArraySum' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts INTEGER_ARRAY ar as parameter.
 */

int simpleArraySum(vector<int> ar) {

}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string ar_count_temp;
    getline(cin, ar_count_temp);

    int ar_count = stoi(ltrim(rtrim(ar_count_temp)));

    string ar_temp_temp;
    getline(cin, ar_temp_temp);

    vector<string> ar_temp = split(rtrim(ar_temp_temp));

    vector<int> ar(ar_count);

    for (int i = 0; i < ar_count; i++) {
        int ar_item = stoi(ar_temp[i]);

        ar[i] = ar_item;
    }

    int result = simpleArraySum(ar);

    fout << result << "\n";

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));

    return tokens;
}

◇Full Solution

『』
CPP
#include <bits/stdc++.h>

using namespace std;

string ltrim(const string &);
string rtrim(const string &);
vector<string> split(const string &);

/*
 * Complete the 'simpleArraySum' function below.
 *
 * The function is expected to return an INTEGER.
 * The function accepts INTEGER_ARRAY ar as parameter.
 */

int simpleArraySum(vector<int> ar) {
    int sum = 0;
    for (int x : ar) sum += x;
    return sum;
}

int main()
{
    ofstream fout(getenv("OUTPUT_PATH"));

    string ar_count_temp;
    getline(cin, ar_count_temp);

    int ar_count = stoi(ltrim(rtrim(ar_count_temp)));

    string ar_temp_temp;
    getline(cin, ar_temp_temp);

    vector<string> ar_temp = split(rtrim(ar_temp_temp));

    vector<int> ar(ar_count);

    for (int i = 0; i < ar_count; i++) {
        int ar_item = stoi(ar_temp[i]);

        ar[i] = ar_item;
    }

    int result = simpleArraySum(ar);

    fout << result << "\n";

    fout.close();

    return 0;
}

string ltrim(const string &str) {
    string s(str);

    s.erase(
        s.begin(),
        find_if(s.begin(), s.end(), not1(ptr_fun<int, int>(isspace)))
    );

    return s;
}

string rtrim(const string &str) {
    string s(str);

    s.erase(
        find_if(s.rbegin(), s.rend(), not1(ptr_fun<int, int>(isspace))).base(),
        s.end()
    );

    return s;
}

vector<string> split(const string &str) {
    vector<string> tokens;

    string::size_type start = 0;
    string::size_type end = 0;

    while ((end = str.find(" ", start)) != string::npos) {
        tokens.push_back(str.substr(start, end - start));

        start = end + 1;
    }

    tokens.push_back(str.substr(start));

    return tokens;
}

◇References & Navigation

02 - Simple Array Sum | PROJECT ENGRAM