敌兵布阵---hud1166（线段树或者树状数组模板）

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=1166

线段树中对某一点的值进行改变；

#include<iostream>
#include<stdio.h>
#include<string.h>
#include<algorithm>
using namespace std;

#define N 50010
#define Lson r<<1
#define Rson r<<1|1

struct SegmentTree
{
    int L, R, k, sum;
    int Mid()
    {
        return (L+R)>>1;
    }
    int len()
    {
        return R-L+1;
    }
}a[N<<2];

void BuildTree(int r,int L,int R)
{
    a[r].L = L; a[r].R = R; a[r].k = 0;
    if(L == R)
    {
        scanf("%d",&a[r].sum);
        return ;
    }

    BuildTree(Lson, L, a[r].Mid());
    BuildTree(Rson, a[r].Mid()+1, R);

    a[r].sum = a[Lson].sum + a[Rson].sum;
}
int Query(int r, int L, int R)
{
    if(a[r].R == R && a[r].L == L)
        return a[r].sum;
    if(L>a[r].Mid())
        return Query(Rson, L, R);
    else if(R <= a[r].Mid())
        return Query(Lson, L, R);
    else
    {
        int sum1=Query(Lson, L, a[r].Mid());
        int sum2=Query(Rson, a[r].Mid()+1, R);
        return sum1 + sum2;
    }
}
void Update(int r, int p, int x)
{
    if(a[r].L == p && a[r].R == p)
    {
        a[r].sum += x;
        return ;
    }

    if(p<=a[r].Mid())
        Update(Lson, p, x);
    else
        Update(Rson, p, x);

    a[r].sum = a[Rson].sum + a[Lson].sum;
}
int main()
{
    int t=1, T, n, L, R, p, x;
    char s[10];
    scanf("%d", &T);
    while(T--)
    {
        scanf("%d", &n);
        BuildTree(1, 1, n);
        printf("Case %d:
", t++);
        while(scanf("%s", s))
        {
            if(s[0] == 'E')break;
            else if(s[0] == 'Q')
            {
                scanf("%d %d", &L, &R);
                printf("%d
", Query(1, L, R));
            }
            else if(s[0] == 'A')
            {
                scanf("%d%d", &p,&x);
                Update(1, p, x);
            }
            else if(s[0] == 'S')
            {
                scanf("%d %d", &p, &x);
                Update(1, p, -x);//减去一个数可以看做加一个负数;
            }
        }
    }
    return 0;
}

关于树状数组：参考链接

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<iostream>

using namespace std;

#define N 50500
#define met(a, b) memset(a, b, sizeof(a))
int Tree[N], n;

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

void Update(int pos, int num)
{
    while(pos<=n)
    {
        Tree[pos]+=num;
        pos += lowbit(pos);
    }
}

int GetSum(int pos)
{
    int s=0;
    while(pos)
    {
        s += Tree[pos];
        pos -= lowbit(pos);
    }
    return s;
}
int main()
{
    int T, t=1;
    scanf("%d", &T);
    while(T--)
    {
        met(Tree, 0);
        int num, pos, x, y;
        scanf("%d", &n);
        for(int i=1; i<=n; i++)
        {
            scanf("%d", &num);
            Update(i, num);
        }
        printf("Case %d:
", t++);
        char s[110];
        while(scanf("%s", s), s[0]!='E')
        {
            if(s[0]=='A')
            {
                scanf("%d %d", &pos, &num);
                Update(pos, num);
            }
            if(s[0]=='S')
            {
                scanf("%d %d", &pos, &num);
                Update(pos, -num);
            }
            if(s[0]=='Q')
            {
                scanf("%d %d", &x, &y);
                int ans = GetSum(y)-GetSum(x-1);
                printf("%d
", ans);
            }
        }
    }
    return 0;
}