树状数组

树状数组

单点修改 区间查询

修改 查询复杂度 \(O(log \ n)\)

int lowbit(x)
{
    return x&-x;
}

void add(int x,int k)
{
    while(x<=n)
    {
        tree[x]+=k;
        x+=lowbit(x);
    }
}

int query(int x)
{
    int ans=0;
    while(x)
    {
        ans+=tree[x];
        x-=lowbit(x);
    }
    return ans;
}

区间修改 单点查询

int lowbit(int x)
{
    return x&-x;
}

void add(int x,int y,int k)
{
    change(x,k);
    change(y+1,-k);
}

void change(int x,int k)
{
    while(x<=n)
    {
        delta[x]+=k;
        x+=lowbit(x);
    }
}

int query(int x)
{
    int sum=0;
    while(x)
    {
        sum+=delta[x];
        x-=lowbit(x);
    }
    return start[x]+sum;
}