区间和【离散化详讲】acwing802

由于坐标太长了，开数组这样的操作是肯定行不通的，离散化的原理就是将没有操作的地方全部抹去，然后再将抹去后的序列求前缀和，即可O(1)时间查询我们需要的区间信息，话不多说，直接上代码吧：

#include
using namespace std;
#define int long long
#define PII pair
#define IOS ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
int n,m,x,c,l,r;
set Point;             //存储所有要用到的点,set用来去重
vector AllPoint;       //存储所有要用到的点
vector add;            //存储要进行累加的操作,first表示位置,second表示加的值
vector Find;           //存储查询的区间,first表示区间l值,second表示区间r值
int a[300005];              //存储最终的离散化操作后的数组
signed main(){
    IOS
    cin>>n>>m;
    for(int i = 1;i <= n;++i)
        cin>>x>>c,Point.insert(x),add.push_back(PII(x,c));
    for(int i = 1;i <= n;++i)
        cin>>l>>r,Point.insert(l),Point.insert(r),Find.push_back(PII(l,r));
    for(auto it : Point)
        AllPoint.push_back(it); //把去重后的点放在AllPoint中
    for(int i = 0,j = add.size();i < j;++i){
        int f = add[i].first,mid;
        l = 0,r = AllPoint.size() - 1;
        while(l <= r){
            mid = l + r >> 1;
            if(AllPoint[mid] < f)   l = mid + 1;
            else if(AllPoint[mid] > f) r = mid - 1;
            else    break;
        }
        a[mid] += add[i].second;
    }
    for(int i = 1,j = AllPoint.size();i < j;++i)
        a[i] += a[i - 1];
    //以上是求前缀和
    for(int i = 0;i < m;++i){
        int f = Find[i].first,t = Find[i].second,mid;
        l = 0,r = AllPoint.size() - 1;
        while(l <= r){
            mid = l + r >> 1;
            if(AllPoint[mid] > f)   r = mid - 1;
            else if(AllPoint[mid] < f)  l = mid + 1;
            else break;
        }
        f = mid;

        l = 0,r = AllPoint.size() - 1;
        while(l <= r){
            mid = l + r >> 1;
            if(AllPoint[mid] > t)   r = mid - 1;
            else if(AllPoint[mid] < t)  l = mid + 1;
            else break;
        }
        t = mid;
        if(f == 0)
            cout<