ZOJ 3279

线段树单点更新

//============================================================================
// Name        : E.cpp
// Author      : L_Ecry
// Version     :
// Copyright   : Your copyright notice
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>
#define N 100050
using namespace std;
int sum[N*4];
int a[N];
void build(int l,int r,int i)
{
    if(l==r)
    {
        sum[i]=a[l];
        return ;
    }
    int mid=(l+r)>>1;
    build(l,mid,i<<1);
    build(mid+1,r,i<<1|1);
    sum[i]=sum[i<<1]+sum[i<<1|1];
}
void update(int l,int r,int p,int va,int i)
{
    if(l==r)
    {
        sum[i]=va;
        return ;
    }
    int mid=(l+r)>>1;
    if(p<=mid)update(l,mid,p,va,i<<1);
    else update(mid+1,r,p,va,i<<1|1);
    sum[i]=sum[i<<1]+sum[i<<1|1];
}
int query(int l,int r,int va,int i)
{
    if(l==r)
    {
        return l;
    }
    int mid=(l+r)>>1;
    if(va<=sum[i<<1])return query(l,mid,va,i<<1);
    else return query(mid+1,r,va-sum[i<<1],i<<1|1);
}
int n,m;
void init()
{
    for(int i=1;i<=n;++i)
        scanf("%d",&a[i]);
    build(1,n,1);
}
void solve()
{
    scanf("%d",&m);
    while(m--)
    {
        char c;
        int x,y;
        scanf(" %c",&c);
        if(c==‘q‘)
        {
            scanf("%d",&x);
            printf("%d\n",query(1,n,x,1));
        }
        else
        {
            scanf("%d%d",&x,&y);
            update(1,n,x,y,1);
        }
    }
}
int main() {
    while(scanf("%d",&n)!=EOF)
    {
        init();
        solve();
    }
    return 0;
}

ZOJ 3279