HDU 1166 敌兵布阵 解题报告 线段树

HDU 1166 敌兵布阵 解题报告 线段树

解题思路：线段树。这道题只是涉及数据结构，跟算法没太大关系，直接看代码就能懂。如果看不懂，去搜线段树的讲解。

#include
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#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#pragma warning(disable:4996)
#define INF 0x3f3f3f3f
#define ll long long
#define PI acos(-1.0)
const int N = 100005;
const int maxn = 1e9;
using namespace std;
int n, t;
int a[50005];
int tree[200020];//tree里放区间和
void build(int id, int l, int r)
{
	if (l == r)
	{
		tree[id] = a[l];
		return;
	}
	int mid = (l + r) >> 1;
	build(id << 1, l, mid);
	build(id << 1 | 1, mid + 1, r);
	tree[id] = tree[id << 1] + tree[id << 1 | 1];
}
int query(int id, int l, int r, int x, int y)
{
	if (x <= l && y >= r)
	{
		return tree[id];
	}
	int mid = (l + r) >> 1;
	int sum = 0;
	if (x <= mid)
		sum += query(id << 1, l, mid, x, y);
	if (y > mid)
		sum += query(id << 1 | 1, mid + 1, r, x, y);
	return sum;
}
void Add(int id, int l, int r, int x, int y)
{
	if (l == r)
	{
		tree[id] += y;
		return;
	}
	int mid = (l + r) >> 1;
	if (x <= mid)
		Add(id << 1, l, mid, x, y);
	else
		Add(id << 1 | 1, mid + 1, r, x, y);
	tree[id] += y;
}
void sub(int id, int l, int r, int x, int y)
{
	if (l == r)
	{
		tree[id] -= y;
		return;
	}
	int mid = (l + r) >> 1;
	if (x <= mid)
		sub(id << 1, l, mid, x, y);
	else
		sub(id << 1 | 1, mid + 1, r, x, y);
	tree[id] -= y;
}
int main()
{
	int cnt = 0;
	scanf("%d", &t);
	while (t--)
	{
		cnt++;
		memset(a, 0, sizeof(a));
		scanf("%d", &n);
		for (int i = 1; i <= n; i++)
		{
			scanf("%d", &a[i]);
		}
		build(1, 1, n);
		printf("Case %d:\n", cnt);
		char ch[10] = "";
		while (scanf("%s", ch))
		{
			if (strcmp(ch, "Query") == 0)
			{
				int x, y;
				scanf("%d%d", &x, &y);
				printf("%d\n", query(1, 1, n, x, y));
			}
			else if (strcmp(ch, "Add") == 0)
			{
				int x, y;
				scanf("%d%d", &x, &y);
				Add(1, 1, n, x, y);
			}
			else if (strcmp(ch, "Sub") == 0)
			{
				int x, y;
				scanf("%d%d", &x, &y);
				sub(1, 1, n, x, y);
			}
			else if (strcmp(ch, "End") == 0)
				break;
			memset(ch, 0, sizeof(0));
		}
	}
}