【codeforces 339D】【线段树奇偶数层次运算pushup】【单点修改】

本文解析了CodeForces上的一道题目,该题要求在给定的(2^n)个数中,更新其中一个值,并交替进行或操作和异或操作,最后得出结果。文章详细介绍了使用线段树进行区间更新和查询的实现过程。

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【链接】

https://codeforces.com/problemset/problem/339/D

【题意】

给你(2^n)个数,更新其中的某个值,交替对这些数进行“或操作”和“异或操作”,得到最终的结果。

【思路】

根据层次分类判断pushup

【代码】代码挺好写的,但是当时做得时候因为看错题目,思路还是有点不清,修改了一下

#include<bits/stdc++.h>
using namespace std;
const int maxn = 1 << 18;
int a[maxn];

struct node {
	int l, r, sum;
	int mid(void) {
		return l + r >> 1;
	}
}tr[maxn<<2];

void build(int p, int l, int r) {
	tr[p].l = l;
	tr[p].r = r;
	tr[p].sum = 0;
	if (l == r)return;
	int mid = tr[p].mid();
	build(p << 1, l, mid);
	build(p << 1 | 1, mid + 1, r);
}

void update(int p, int pos, int x, int cur) {
	if (tr[p].l == tr[p].r) {
		tr[p].sum = x;
		return;
	}
	int mid = tr[p].mid();
	if (pos <= mid)update(p << 1, pos, x, cur - 1);
	else update(p << 1 | 1, pos, x, cur - 1);
	if (cur % 2 == 0) {
		tr[p].sum = tr[p << 1].sum | tr[p << 1 | 1].sum;
	}
	else {
		tr[p].sum = tr[p << 1].sum ^ tr[p << 1 | 1].sum;
	}
}

int main() {
	int n, m, num;
	while (~scanf("%d%d", &n, &m)) {
		num = 1 << n;
		build(1, 1, num);
		for (int i = 1; i <= num; i++) {
			int x;
			scanf("%d", &x);
			update(1, i, x, n + 1);
			
		}
		while (m--) {
			int p, b;
			scanf("%d%d", &p, &b);
			update(1, p, b, n + 1);printf("%d\n", tr[1].sum);
		}
	}
}

 

 

### Codeforces 1487D Problem Solution The problem described involves determining the maximum amount of a product that can be created from given quantities of ingredients under an idealized production process. For this specific case on Codeforces with problem number 1487D, while direct details about this exact question are not provided here, similar problems often involve resource allocation or limiting reagent type calculations. For instance, when faced with such constraints-based questions where multiple resources contribute to producing one unit of output but at different ratios, finding the bottleneck becomes crucial. In another context related to crafting items using various materials, it was determined that the formula `min(a[0],a[1],a[2]/2,a[3]/7,a[4]/4)` could represent how these limits interact[^1]. However, applying this directly without knowing specifics like what each array element represents in relation to the actual requirements for creating "philosophical stones" as mentioned would require adjustments based upon the precise conditions outlined within 1487D itself. To solve or discuss solutions effectively regarding Codeforces' challenge numbered 1487D: - Carefully read through all aspects presented by the contest organizers. - Identify which ingredient or component acts as the primary constraint towards achieving full capacity utilization. - Implement logic reflecting those relationships accurately; typically involving loops, conditionals, and possibly dynamic programming depending on complexity level required beyond simple minimum value determination across adjusted inputs. ```cpp #include <iostream> #include <vector> using namespace std; int main() { int n; cin >> n; vector<long long> a(n); for(int i=0;i<n;++i){ cin>>a[i]; } // Assuming indices correspond appropriately per problem statement's ratio requirement cout << min({a[0], a[1], a[2]/2LL, a[3]/7LL, a[4]/4LL}) << endl; } ``` --related questions-- 1. How does identifying bottlenecks help optimize algorithms solving constrained optimization problems? 2. What strategies should contestants adopt when translating mathematical formulas into code during competitive coding events? 3. Can you explain why understanding input-output relations is critical before implementing any algorithmic approach? 4. In what ways do prefix-suffix-middle frameworks enhance model training efficiency outside of just tokenization improvements? 5. Why might adjusting sample proportions specifically benefit models designed for tasks requiring both strong linguistic comprehension alongside logical reasoning skills?
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