树状数组

#include <iostream>
using namespace std;
const int N = 1E5 + 10;
int tr[N];
int lowbit(int x){
    return x & -x;
}   
void add(int index, int x){
    for(int i = index; i < N; i += lowbit(i))   tr[i] += x;
}
int query(int index){
    int sum = 0;
    for(int i = index; i ; i -= lowbit(i))  sum += tr[i];
    return sum;
}
int main(){
    int n, m;   cin >> n >> m;
    for(int i = 1; i <= n; i ++ ){
        int tmp;    cin >> tmp;
        add(i, tmp);    
    }
    while(m -- ){
        int k, a, b;    cin >> k >> a >> b;
        if(k)   add(a, b);
        else    cout << query(b) - query(a - 1) << endl;
    }
    return 0;
}

线段树

#include <iostream>
#include <cstdio>
using namespace std;
const int N = 1E5 + 10;
struct node{
    int l, r;
    int sum;
}tr[N * 4];
int w[N];
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[l]};
    else{
        tr[u] = {l, r};
        int mid = l + r >> 1;
        build(u << 1, l, mid);
        build(u << 1 | 1, mid + 1, r);
        pushup(u);
    }
}
void modify(int u, int index, int x){
    if(tr[u].l == tr[u].r)  tr[u].sum += x;
    else{
        int mid = tr[u].l + tr[u].r >> 1;
        if(index <= mid)    modify(u << 1, index, x);
        else    modify(u << 1 | 1, index, x);
        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;
}
int main(){
    int n, m;   cin >> n >> m;
    for(int i = 1; i <= n; i ++ )   scanf("%d", &w[i]);
    build(1, 1, n);
    while(m -- ){
        int k, a, b;    scanf("%d%d%d", &k, &a, &b);
        if(k)   modify(1, a, b);
        else    cout << query(1, a, b) << endl;
    }
    return 0;
}