【codeforces 546A】Soldier and Bananas

我不是女神ヾ 2021-10-26 17:18 246阅读 0赞

time limit per test1 second  
memory limit per test256 megabytes  
inputstandard input  
outputstandard output  
A soldier wants to buy w bananas in the shop. He has to pay k dollars for the first banana, 2k dollars for the second one and so on (in other words, he has to pay i·k dollars for the i-th banana).

He has n dollars. How many dollars does he have to borrow from his friend soldier to buy w bananas?

Input  
The first line contains three positive integers k, n, w (1  ≤  k, w  ≤  1000, 0 ≤ n ≤ 109), the cost of the first banana, initial number of dollars the soldier has and number of bananas he wants.

Output  
Output one integer — the amount of dollars that the soldier must borrow from his friend. If he doesn’t have to borrow money, output 0.

Examples  
input  
3 17 4  
output  
13

【题目链接】:[http://codeforces.com/contest/546/problem/A][http_codeforces.com_contest_546_problem_A]

【题解】  
  
就是w个数的等差数列的求和公式。  
然后如果钱够的话输出的是0！！！！  
否则输出差的绝对值就好.  
细心。  
  
【完整代码】

#include <bits/stdc++.h>
    using namespace std;
    #define lson l,m,rt<<1
    #define rson m+1,r,rt<<1|1
    #define LL long long
    #define rep1(i,a,b) for (int i = a;i <= b;i++)
    #define rep2(i,a,b) for (int i = a;i >= b;i--)
    #define mp make_pair
    #define pb push_back
    #define fi first
    #define se second
    #define rei(x) scanf("%d",&x)
    #define rel(x) scanf("%I64d",&x)
    
    typedef pair<int,int> pii;
    typedef pair<LL,LL> pll;
    
    //const int MAXN = x;
    const int dx[9] = {
         0,1,-1,0,0,-1,-1,1,1};
    const int dy[9] = {
         0,0,0,-1,1,-1,1,-1,1};
    const double pi = acos(-1.0);
    
    LL k,n,w;
    
    int main()
    {
        //freopen("F:\\rush.txt","r",stdin);
        rel(k);rel(n);rel(w);
        LL temp1 = (k + w*k)*w/2;
        LL temp = n-temp1;
        if (temp <0)
            cout << abs(temp)<<endl;
        else
            puts("0");
        return 0;
    }

转载于:https://www.cnblogs.com/AWCXV/p/7626763.html

[http_codeforces.com_contest_546_problem_A]: http://codeforces.com/contest/546/problem/A