HDU 1698 Just a Hook (线段树)

http://acm.hdu.edu.cn/showproblem.php?pid=1698

/*843ms,2288KB*/

#include <cstdio>
#include <algorithm>
using namespace std;
#define lson l , m , rt << 1
#define rson m + 1 , r , rt << 1 | 1
#define root 1, n, 1
const int maxn = 100000;

int sum[maxn << 2], cache[maxn << 2];

inline void pushup(int rt)
{
	sum[rt] = sum[rt << 1] + sum[rt << 1 | 1];
}

inline void pushdown(int rt, int m)
{
	if (cache[rt])
	{
		cache[rt << 1] = cache[rt << 1 | 1] = cache[rt];///更新左右子区间cache
		sum[rt << 1] = (m - (m >> 1)) * cache[rt];
		sum[rt << 1 | 1] = (m >> 1) * cache[rt];///平分cache，更新左右子区间和
		cache[rt] = 0;
	}
}

void build(int l, int r, int rt)
{
	cache[rt] = 0;
	sum[rt] = 1;
	if (l == r) return;
	int m = (l + r) >> 1;
	build(lson);
	build(rson);
	pushup(rt);
}

void update(int ql, int qr, int c, int l, int r, int rt)
{
	if (ql <= l && r <= qr)
	{
		cache[rt] = c;
		sum[rt] = c * (r - l + 1);
		return;
	}
	///打开上层acahe，往下细分计算
	pushdown(rt , r - l + 1);
	int m = (l + r) >> 1;
	if (ql <= m) update(ql , qr , c , lson);
	if (qr > m) update(ql , qr , c , rson);
	pushup(rt);
}

int main()
{
	int T, n, m, a, b, c;
	scanf("%d", &T);
	for (int cas = 1 ; cas <= T ; cas ++)
	{
		scanf("%d%d", &n, &m);
		build(root);
		while (m--)
		{
			scanf("%d%d%d", &a, &b, &c);
			update(a, b, c, root);
		}
		printf("Case %d: The total value of the hook is %d.\n", cas, sum[1]);
	}
	return 0;
}