【模板】cdq分治代替树状数组（单点修改，区间查询）

#include 
#include 
#include 
#include 
#include 
#include 
using namespace std;
const int N = (int)1e6 + 5;

int n, m;
struct Q{
    int type, id;
    long long val;
    friend bool operator < (Q x, Q y){
        return x.id == y.id ? x.type < y.type : x.id < y.id;
    }
}q[N], tmp[N];
int qsize;
long long ans[N];
int asize;

void cdq(int l, int r){//左闭右开
    if(r - l <= 1) return ;//长度为1的区间内部就不会有贡献了
    int mid = l + ((r - l) >> 1);
    cdq(l, mid); cdq(mid, r);
    long long sum = 0;
    int i = l, j = mid, tsize = 0;
        //合并并计算左区间对右区间贡献
    while(i < mid && j < r){
        if(q[i] < q[j]){
            if(q[i].type == 1) sum += q[i].val;
            tmp[++tsize] = q[i++];  
        }
        else {
            if(q[j].type == 2) ans[q[j].val] -= sum;
            else if(q[j].type == 3) ans[q[j].val] += sum;
            tmp[++tsize] = q[j++];
        }
    }
    while(i < mid) tmp[++tsize] = q[i++];
    while(j < r){
        if(q[j].type == 2) ans[q[j].val] -= sum;
        else if(q[j].type == 3) ans[q[j].val] += sum;
        tmp[++tsize] = q[j++];
    }
    for(int i = 1; i <= tsize; ++i) q[l + i - 1] = tmp[i];
}

/*
这部分的思路总结

判断是否到边界
下方左右分治
计算左边对右边的贡献
把左右类似归并排序重排

*/

int main() {
    scanf("%d%d", &n, &m);
    for(int i = 1; i <= n; ++i){
        ++qsize;
        q[qsize].id = i, q[qsize].type = 1;
        scanf("%lld", &q[qsize].val);
    }
    for(int i = 1; i <= m; ++i){
        scanf("%d", &q[++qsize].type);
        if(q[qsize].type == 1){
            scanf("%d%lld", &q[qsize].id, &q[qsize].val);
        }
        else {
            int l, r; scanf("%d%d", &l, &r);
            ++asize;
            q[qsize].id = l - 1, q[qsize].val = asize;
            q[++qsize].id = r, q[qsize].type = 3, q[qsize].val = asize;
        }
    }
    cdq(1, qsize + 1);
    for(int i = 1; i <= asize; ++i) printf("%lld\n", ans[i]); 
    return 0;    
}

转载于:https://www.cnblogs.com/hjmmm/p/10507736.html