线段树和树状数组的分析和理解

1264. 动态求连续区间和

````

树状数组写法
#include[HTML_REMOVED]
using namespace std;
const int N=1e5+10;
int q[N],tr[N];
int n,m;
int lowbit(int x){
return x & -x;
}
int query(int x){
int res=0;
for(int i=x;i;i-=lowbit(i))res+=tr[i];
return res;
}
void add(int x,int y){
for(int i=x;i<=n;i+=lowbit(i))tr[i]+=y;
}
int main(){
cin>>n>>m;
for(int i=1;i<=n;i)cin>>q[i];
for(int i=1;i<=n;i)add(i,q[i]);
for(int i=0;i[HTML_REMOVED]>k>>x>>y;
if(k==0){
cout<<query(y)-query(x-1)<<endl;
}else{
add(x,y);
}
}
return 0;
}
````

线段树写法
//鼠标没带……ACwing的代码不支持自动滑轮的操作只能先粘贴Y总的代码~~~
#include [HTML_REMOVED]

include [HTML_REMOVED]

include [HTML_REMOVED]

include [HTML_REMOVED]

using namespace std;

const int N = 100010;

int n, m;
int w[N];
struct Node
{
int l, r;
int sum;
}tr[N * 4];

void pushup(int u)
{
tr[u].sum = tr[u << 1].sum + tr[u << 1 | 1].sum;
}

void build(int u, int l, int r)
{
if (l == r) tr[u] = {l, r, w[r]};
else
{
tr[u] = {l, r};
int mid = l + r >> 1;
build(u << 1, l, mid), build(u << 1 | 1, mid + 1, r);
pushup(u);
}
}

int query(int u, int l, int r)
{
if (tr[u].l >= l && tr[u].r <= r) return tr[u].sum;
int mid = tr[u].l + tr[u].r >> 1;
int sum = 0;
if (l <= mid) sum = query(u << 1, l, r);
if (r > mid) sum += query(u << 1 | 1, l, r);
return sum;
}

void modify(int u, int x, int v)
{
if (tr[u].l == tr[u].r) tr[u].sum += v;
else
{
int mid = tr[u].l + tr[u].r >> 1;
if (x <= mid) modify(u << 1, x, v);
else modify(u << 1 | 1, x, v);
pushup(u);
}
}

int main()
{
scanf(“%d%d”, &n, &m);
for (int i = 1; i <= n; i ++ ) scanf(“%d”, &w[i]);
build(1, 1, n);

int k, a, b;
while (m -- )
{
    scanf("%d%d%d", &k, &a, &b);
    if (k == 0) printf("%d\n", query(1, a, b));
    else modify(1, a, b);
}

return 0;

}

作者：yxc
链接：https://www.acwing.com/activity/content/code/content/168768/
来源：AcWing