洛谷 P1198 [JSOI2008]最大数

最大数

此题是一道适合线段树初学者拿来练手的好题，不需要过多的复杂操作（如pushdown, lazy tag等）。

此题需要做的只是在末尾加点和区间查询最大值操作即可。

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Code：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;
//Mystery_Sky
//
#define M 1000005
#define maxn 1000010
#define ll long long
#define Mid (l+r)>>1
struct Tree{
	int x;
	Tree *lc, *rc;
}dizhi[M<<1], *root = &dizhi[0];

int m, d, t=0, T;

void build(Tree *tree, int l, int r)
{
	if(l == r) {
		tree->x = 0;
		return;
	}
	int mid = Mid;
	tree->lc = &dizhi[++t];
	tree->rc = &dizhi[++t];
	build(tree->lc, l, mid);
	build(tree->rc, mid+1, r);
	tree->x = max(tree->lc->x, tree->rc->x);
}

void update(Tree *tree, int l, int r, int x, int d)
{
	if(l == r) {
		tree->x = d;
		return;
	}
	int mid = Mid;
	if(x <= mid) update(tree->lc, l, mid, x, d);
	else update(tree->rc, mid+1, r, x, d);
	tree->x = max(tree->lc->x, tree->rc->x);	
}

int query(Tree *tree, int l, int r, int x, int y) 
{
	if(x <= l && y >= r) return tree->x;
	int mid = Mid;
	int ans = 0;
	if(x <= mid) ans = max(ans, query(tree->lc, l, mid, x, y));
	if(y > mid) ans = max(ans, query(tree->rc, mid+1, r, x, y));
	return ans;
}

int main() {
	scanf("%d%d", &m, &d);
	int n = 1000000;
	build(root, 1, n);
	char a;
	int b;
	int num = 0;
	for(int i = 1; i <= m; i++) {
		cin >> a >> b;
		if(a == 'A') {
			num++;
			update(root, 1, n, num, (b + T)%d);
		}
		if(a == 'Q') {
			T = query(root, 1, n, num-b+1, num);
			printf("%d\n", T);
		}
	}
	return 0;
}