【离散化】acwing802. 区间和

802. 区间和 - AcWing题库

C++ pair的基本用法总结（整理）_sevenjoin的博客-CSDN博客_c++ pair

for(auto i : v)遍历容器元素 - ostartech - 博客园 (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;//返回值从1开始，便于后续求前缀和
}

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中不重复的数

    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());

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

    // 预处理前缀和
    for (int i = 1; i <= alls.size(); i ++ ) s[i] = s[i - 1] + a[i];

    // 处理询问
    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
链接：https://www.acwing.com/activity/content/code/content/40105/
来源：AcWing
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

也可以这样：

#include<bits/stdc++.h>
#define rep(i,a,b)  for(int i=a;i<=b;i++)
using namespace std;
const int N=3e5+10;
typedef pair<int,int> PII;
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;
}
int main(){
    int n,m,x,c,l,r;
    cin>>n>>m;
    rep(i,0,n-1){
        cin>>x>>c;
        add.push_back({x,c});
        alls.push_back(x);
    }
    rep(i,0,m-1){
        cin>>l>>r;
        query.push_back({l,r});
        alls.push_back(l);
        alls.push_back(r);
    }
    sort(alls.begin(),alls.end());
    alls.erase(unique(alls.begin(),alls.end()),alls.end());//改为使用自带库函数unique
    for(auto item:add){
        int x=find(item.first);
        a[x]+=item.second;
    }
    rep(i,1,alls.size()) s[i]=s[i-1]+a[i];
    for(auto item:query){
        int l=find(item.first),r=find(item.second);
        cout<<s[r]-s[l-1]<<endl;
    }
    return 0;
}