HDU 1166（线段树）

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

区间求和问题~~~

代码如下：

#include <stdio.h>
#include <string.h>
#define N 50002
#define L(x) ((x)<<1)
#define R(x) ((x)<<1|1)

typedef struct
{
    int lson, rson;
    int val;
} seg_tree;

seg_tree s[N<<2];
int a[N];

int build(int left, int right, int idx)
{
    s[idx].lson = left;
    s[idx].rson = right;
    if(left == right)
    {
        s[idx].val = a[left];
        return a[left];
    }
    int mid = (left + right) / 2;
    return s[idx].val = (build(left, mid, L(idx)) + build(mid + 1, right, R(idx)));
}

void update(int id, int idx, int val)
{
    s[idx].val += val;
    if(s[idx].lson == s[idx].rson)
    {
        return;
    }
    int mid = (s[idx].lson + s[idx].rson) / 2;
    if(id <= mid)
    {
        update(id, L(idx), val);
    }
    else
    {
        update(id, R(idx), val);
    }
}

int query(int left, int right, int idx)
{
    if(left == s[idx].lson && s[idx].rson == right)
    {
        return s[idx].val;
    }
    int mid = (s[idx].lson + s[idx].rson) / 2;
    if(right <= mid)
    {
        return query(left, right, L(idx));
    }
    else if(left > mid)
    {
        return query(left, right, R(idx));
    }
    else
    {
        return query(left, mid, L(idx)) + query(mid + 1, right, R(idx));
    }
}

int main()
{
    int t;
    int n;
    int i, j;
    char str[10];
    scanf("%d", &t);
    for(i = 1; i <= t; i++)
    {
        scanf("%d", &n);
        for(j = 1; j <= n; j++)
        {
            scanf("%d", &a[j]);
        }
        build(1, n, 1);
        printf("Case %d:\n", i);
        while(scanf("%s", str) != EOF)
        {
            if(!strcmp(str, "End"))
            {
                break;
            }
            int c, d;
            scanf("%d%d", &c, &d);
            switch(str[0])
            {
                case 'A':
                    update(c, 1, d);
                    break;
                case 'S':
                    update(c, 1, -d);
                    break;
                case 'Q':
                    printf("%d\n", query(c, d, 1));
                    break;
            }
        }
    }
}