백준 알고리즘 11659번 : 구간 합 구하기 4

링크

https://www.acmicpc.net/problem/11659

sol1) prefix sum

#pragma GCC optimize("O3")
#pragma GCC optimize("Ofast")
#pragma GCC optimize("unroll-loops")
#include<bits/stdc++.h>
#define X first
#define Y second
#define pb push_back
#define fastio cin.tie(0)->sync_with_stdio(0)
#define sz(v) (int)(v).size()
#define all(v) v.begin(), v.end()
#define rall(v) (v).rbegin(), (v).rend()
#define compress(v) sort(all(v)), (v).erase(unique(all(v)), (v).end())
#define OOB(x, y) ((x) < 0 || (x) >= n || (y) < 0 || (y) >= m)
#define debug(x) cout << (#x) << ": " << (x) << '\n'
using namespace std;
using ll = long long;
using ull = unsigned long long;
using dbl = double;
using ldb = long double;
using pii = pair<int,int>;
using pll = pair<ll,ll>;
using vi = vector<int>;
using vs = vector<string>;
using tii = tuple<int,int,int>;
template<typename T> using wector = vector<vector<T>>;

const int MOD = 1e9 + 7;
const int INF = 1e9 + 7;
const ll LNF = 1e18 + 7;

int v[100'001],pSum[100'001];

int main() {
  fastio;
  int n,m; cin >> n >> m;
  for(int i = 1; i <= n; i++)cin >> v[i];
  pSum[1] = v[1];
  for(int i = 1; i <= n; i++) pSum[i] = v[i] + pSum[i - 1];
  while(m--){
    int s,e; cin >> s >> e;
    cout << pSum[e] - pSum[s - 1] << "\n";
  }
  return 0;
}

prefix sum 연습 문제입니다.
누적합을 이용해서 쿼리를 해결해주면 됩니다.
예를 들어 구간 [s,e]의 합을 구하고 싶다면 p[e] - p[s - 1]을 해주면 됩니다.