swust oj 2474 F(k)

本文介绍了一种通过暴力解法结合二分查找技术来解决特定数列问题的方法。问题的核心在于给定一个特殊的不降序列,需要快速定位并找出序列中指定位置的数值。

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【题意】

小明有一个不降序列(f(1),f(2),f(3),……),f(k)代表在这个序列中大小是k的有f(k)个。我们规定f(n)的前12项如下图。
n           1    2    3    4    5   6   7   8   9   10   11   12

f(n)        1    2    2    3    3   4   4   4   5   5    5    6
 
现在给你一个n,你知道f(n)是多少吗?
【解题思路】

暴力,看懂题意之后暴力解决这个问题。更快的效率是,求前缀和,然后二分位置。坑点,本oj这个题不能单组输入。

【AC代码】


#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
using namespace std;
#define ll long long
ll a[20000000];
ll cnt=4;
void Init()
{
    memset(a,0,sizeof(a));
    a[1]=1;
    a[2]=2;
    a[3]=2;
    for(ll i=3; i<=10000; i++)
    {
        for(ll j=1; j<=a[i]; j++)
        {
            a[cnt++] = i;
        }
        if(a[cnt]>800000)break;
    }
}
int main()
{
    Init();
    ll n;
    while(~scanf("%I64d",&n))
    {

        ll ans=0;
        int pos;
        for(int i=1; i<=cnt; i++)
        {
            ans += a[i];
            if(ans>=n)
            {
                pos = i;
                break;
            }
        }
        printf("%d\n",pos);
    }
    return 0;
}


### SWUST OJ Problem 32 Information and Solution Unfortunately, specific details about SWUST OJ problem number 32 are not directly provided in the available references. However, based on similar problems from this platform such as those mentioned in other citations, a general approach to solving typical programming challenges can be outlined. #### Understanding Common Elements of Programming Problems on SWUST OJ Platform Problems like SWUSTOJ276, SWUSTOJ77, SWUSTOJ78, SWUSTOJ1286, and SWUSTOJ1285 emphasize proper use of `if` and `else` statements along with maintaining good coding practices including appropriate formatting[^1]. For instance, when dealing with numerical outputs, `%g` is used for automatic selection between fixed-point notation (`%f`) or scientific notation (`%e`), depending on which provides more compact output without loss of precision. Given that detailed specifics regarding problem 32 aren't present here, one should look at common patterns found across different types of questions posed by platforms like these: - **Input Handling**: Typically involves reading inputs either single values or arrays/lists. - **Logic Implementation**: Applying algorithms ranging from simple arithmetic operations up through complex data structures manipulation. - **Output Formatting**: Ensuring results adhere strictly to specified formats using placeholders like `%d`, `%s`, etc., where applicable. Since no direct reference exists specifically addressing SWUST OJ problem 32 within given sources, consider exploring adjacent numbered problems around it for clues about its nature—whether mathematical computation, string processing, dynamic programming elements, et cetera—and adapt solutions accordingly while keeping best practice guidelines intact. ```c // Example C code snippet demonstrating basic structure often seen in contest-style programs #include <stdio.h> int main() { int n; scanf("%d", &n); // Read input value if (condition_based_on_problem_statement) { printf("Result under condition A\n"); } else { printf("Alternative result\n"); } return 0; } ``` --related questions-- 1. How does understanding how `%g` works help improve program efficiency? 2. What strategies could apply towards optimizing performance in competitive programming contests? 3. Can you provide examples illustrating effective usage of conditional operators (`if`, `else`) in algorithm design?
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