codeforces 401A Vanya and Cards

探讨了Vanya如何通过找到最少数量的卡片使卡片数值总和为零的问题。输入包含已找到卡片的数量及最大绝对值限制,输出则为达到平衡所需的最小额外卡片数。

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A. Vanya and Cards
time limit per test
1 second
memory limit per test
256 megabytes
input
standard input
output
standard output

Vanya loves playing. He even has a special set of cards to play with. Each card has a single integer. The number on the card can be positive, negative and can even be equal to zero. The only limit is, the number on each card doesn't exceed x in the absolute value.

Natasha doesn't like when Vanya spends a long time playing, so she hid all of his cards. Vanya became sad and started looking for the cards but he only found n of them. Vanya loves the balance, so he wants the sum of all numbers on found cards equal to zero. On the other hand, he got very tired of looking for cards. Help the boy and say what is the minimum number of cards does he need to find to make the sum equal to zero?

You can assume that initially Vanya had infinitely many cards with each integer number from  - x to x.

Input

The first line contains two integers: n (1 ≤ n ≤ 1000) — the number of found cards and x (1 ≤ x ≤ 1000) — the maximum absolute value of the number on a card. The second line contains n space-separated integers — the numbers on found cards. It is guaranteed that the numbers do not exceed x in their absolute value.

Output

Print a single number — the answer to the problem.

Examples
input
3 2
-1 1 2
output
1
input
2 3
-2 -2
output
2
Note

In the first sample, Vanya needs to find a single card with number -2.

In the second sample, Vanya needs to find two cards with number 2. He can't find a single card with the required number as the numbers on the lost cards do not exceed 3 in their absolute value.


题挺简单的,但是读不懂题意,唉~~,还是阅读不够好。

#include<bits/stdc++.h>
using namespace std;
int main()
{
    int n,x,w;
    cin>>n>>x;
    int sum=0;
    for(int i=0;i<n;i++)
    {
    	cin>>w;
    	sum+=w;
    }
    if(sum<0)
    	sum=-sum;
    if(sum%x==0)
    	cout<<sum/x<<endl;
    else
    	cout<<sum/x+1<<endl;
    return 0;
}



虽然给定引用中未直接提及“Kuroni and Simple Strings”题目的详细信息,但通常这类题目可能与字符串处理、括号匹配等相关。一般而言,题目可能会给出一个由括号组成的字符串,要求找出能移除的最大数量的不相交的合法括号对,并输出移除这些括号对后的相关信息。 ### 解法分析 #### 栈解法 栈解法是处理括号匹配问题的经典方法。通过遍历字符串,将左括号压入栈中,遇到右括号时,若栈顶为左括号,则将栈顶元素弹出,表示这是一对匹配的括号。 ```python s = input() stack = [] pairs = [] for i, char in enumerate(s): if char == '(': stack.append(i) else: if stack: left_index = stack.pop() pairs.append((left_index + 1, i + 1)) if not pairs: print(0) else: print(1) print(len(pairs) * 2) result = [] for l, r in pairs: result.extend([l, r]) result.sort() print(" ".join(map(str, result))) ``` #### 双指针解法 双指针解法从字符串的两端向中间遍历,分别使用两个指针 `left` 和 `right`。`left` 指针从左向右寻找 `(`,`right` 指针从右向左寻找 `)`,当找到一对匹配的括号时,将它们标记为已移除,继续寻找下一对匹配的括号,直到无法再找到匹配的括号为止。 ```python s = input() n = len(s) left = 0 right = n - 1 pairs = [] while left < right: while left < right and s[left] != '(': left += 1 while left < right and s[right] != ')': right -= 1 if left < right: pairs.append((left + 1, right + 1)) left += 1 right -= 1 if not pairs: print(0) else: print(1) print(len(pairs) * 2) result = [] for l, r in pairs: result.extend([l, r]) result.sort() print(" ".join(map(str, result))) ``` ### 复杂度分析 - **栈解法**:时间复杂度为 $O(n)$,其中 $n$ 是字符串的长度。空间复杂度为 $O(n)$,主要用于栈的空间开销。 - **双指针解法**:时间复杂度为 $O(n)$,空间复杂度为 $O(n)$,主要用于存储匹配的括号对。
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