802. 區間和 - AcWing題庫

C++ pair的基本用法總結（整理）_sevenjoin的部落格-CSDN部落格_c++ pair

for(auto i : v)遍歷容器元素 - ostartech - 部落格園 (cnblogs.com)

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

typedef pair<int, int> PII;

const int N = 300010;

int n, m;
int a[N], s[N];

vector
 
<int> alls;
vector<PII> add, query;

int find(int x)
{
    int l = 0, r = alls.size() - 1;
    while (l < r)
    {
        int mid = l + r >> 1;
        if (alls[mid] >= x) r = mid;
        else l = mid + 1;
    }
    return r + 1;//返回值從1開始，便於後續求字首和
}

vector<int>::iterator unique(vector<int
 
> &a)
{
    int j = 0;
    for (int i = 0; i < a.size(); i ++ )
        if (!i || a[i] != a[i - 1])
            a[j ++ ] = a[i];
    // a[0] ~ a[j - 1] 所有a中不重複的數

    return a.begin() + j;
}

int main()
{
    cin >> n >> m;
    for (int i = 0; i < n; i ++ )
    {
        int x, c;
        cin 
 
>> x >> c;
        add.push_back({x, c});

        alls.push_back(x);
    }

    for (int i = 0; i < m; i ++ )
    {
        int l, r;
        cin >> l >> r;
        query.push_back({l, r});

        alls.push_back(l);
        alls.push_back(r);
    }

    // 去重
    sort(alls.begin(), alls.end());
    alls.erase(unique(alls), alls.end());

    // 處理插入
    for (auto item : add)
    {
        int x = find(item.first);
        a[x] += item.second;
    }

    // 預處理字首和
    for (int i = 1; i <= alls.size(); i ++ ) s[i] = s[i - 1] + a[i];

    // 處理詢問
    for (auto item : query)
    {
        int l = find(item.first), r = find(item.second);
        cout << s[r] - s[l - 1] << endl;
    }

    return 0;
}

作者：yxc
連結：https://www.acwing.com/activity/content/code/content/40105/
來源：AcWing
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