POJ 3468 - A Simple Problem with Integers

線段樹成段更新，更新和查詢利用延遲標記，不需要更新到葉子結點。
當要更新或查詢的路徑上遇到了延遲標記，則需要將此標記更新到子結點即可。

#include <stdio.h>
#include <string.h>
#define lson rt << 1
#define rson rt << 1 | 1
long long maxn[100002 << 2], lazy[100002 << 2];
void build(int l, int r, int rt)
{
    if(l == r)
    {
        scanf("%I64d", &maxn[rt]);
        return ;
    }
    int mid = (l + r) >> 1;
    build(l, mid, lson);
    build(mid + 1, r, rson);
    maxn[rt] = maxn[lson] + maxn[rson];
}
long long query(int l, int r, int rt, int L, int R)
{
    if(L <= l && R >= r)
    {
        return maxn[rt];
    }
    int mid = (l + r) >> 1;
    if(lazy[rt])
    {
        lazy[lson] += lazy[rt];
        lazy[rson] += lazy[rt];
        maxn[lson] += (long long)(mid - l + 1) * lazy[rt];
        maxn[rson] += (long long)(r - mid) * lazy[rt];
        lazy[rt] = 0;
    }
    long long ans = 0;
    if(L <= mid) ans = query(l, mid, lson, L, R);
    if(R > mid) ans += query(mid + 1, r, rson, L, R);
    return ans;
}
void update(int l, int r, int rt, int L, int R, int val)
{
    if(L <= l && R >= r)
    {
        maxn[rt] += (long long)(r - l + 1) * val;
        lazy[rt] += val;
        return ;
    }
    int mid = (l + r) >> 1;
    if(lazy[rt])
    {
        lazy[lson] += lazy[rt];
        lazy[rson] += lazy[rt];
        maxn[lson] += (long long)(mid - l + 1) * lazy[rt];
        maxn[rson] += (long long)(r - mid) * lazy[rt];
        lazy[rt] = 0;
    }
    if(L <= mid) update(l, mid, lson, L, R, val);
    if(R > mid) update(mid + 1, r, rson, L, R, val);
    maxn[rt] = maxn[lson] + maxn[rson];
}
int main()
{
    int N, Q;
    char ch[10];
    while(~scanf("%d %d", &N, &Q))
    {
        build(1, N, 1);
        memset(lazy, 0, sizeof(lazy));
        for(int i = 0; i < Q; i++)
        {
            int x, y, z;
            scanf("%s", ch);
            if(ch[0] == 'Q')
            {
                scanf("%d %d", &x, &y);
                printf("%I64d\n", query(1, N, 1, x, y));
            }
            else
            {
                scanf("%d %d %d", &x, &y, &z);
                update(1, N, 1, x, y, z);
            }
        }
    }
    return 0;
}