PAT A1009 Product of Polynomials(25)

题意

• 模拟多项式相乘。

注意

1. 不会有零项。
2. 开一个2*MAX-1的数组存放结果。
3. memset过检测需要加头文件cstring
4. scanf读取double类型需要%lf

代码

#include <iostream>
#include <cstring>
using namespace std;

const int MAX = 1001;
double n1[MAX];
double n2[MAX];
double p[2*MAX-1];
bool b1[MAX];
bool b2[MAX];
int k1, k2;

void product()
{
	for (int i = 0; i < MAX; i++)
	{
		if (!b1[i])
			continue;
		for (int j = 0; j < MAX; j++)
		{
			if (!b2[j])
				continue;
			p[i + j] += n1[i] * n2[j];
		}
	}
	int c = 0;
	for (int i = 0; i < 2 * MAX - 1; i++)
		if (p[i] != 0)
			c++;
	printf("%d", c);
	for (int i = 2 * MAX - 2; i >= 0; i--)
		if (p[i] != 0)
			printf(" %d %.1f", i, p[i]);
}

int main()
{
	fill(b1, b1 + MAX, false);
	fill(b2, b2 + MAX, false);    //每个元素赋值   区间[a,b)
	memset(p, 0, sizeof p);       //每个字节赋值   头文件 cstring

	int n;
	scanf_s("%d", &k1);
	for (int i = 0; i < k1; i++)
	{
		scanf_s("%d", &n);
		scanf_s("%lf", &n1[n]);   //scanf读取double要用 "%lf" , printf不区分
		b1[n] = true;
	}
	
	scanf_s("%d", &k2);
	for (int i = 0; i < k2; i++)
	{
		scanf_s("%d", &n);
		scanf_s("%lf", &n2[n]);
		b2[n] = true;
	}
	product();
	
    return 0;
}

再来一个。。

#include <iostream>
#include <cstring>                   //要不用不了memset()
#include <algorithm>
using namespace std;

const int MAX = 11;
int k1, k2;

struct ss
{
	int e;
	double co;
};

ss s1[MAX], s2[MAX], s3[MAX*MAX];

bool cmp(const ss s1, const ss s2)
{
	return s1.e > s2.e;
}

void product()
{
	int x = 0;
	for (int i = 0; i < k1; i++)
	{
		for (int j = 0; j < k2; j++)
		{
			s3[x].co = s1[i].co * s2[j].co;
			s3[x++].e = s1[i].e + s2[j].e;
		}
	}
	sort(s3, s3 + x, cmp);

	//1
	int x0 = 0;
	for (int i = 0; i < x;)
	{
		for (int j = i + 1;;)
		{
			if (j < x && s3[i].e == s3[j].e)
			{
				s3[i].co += s3[j].co;
				j++;
			}
			else
			{
				if (s3[i].co != 0.0)                          //  先乘后加的过程，乘的时候不会有，加的时候肯定会有系数为0的情况
				{                                             //  19.3.6
					s3[x0].e = s3[i].e;
					s3[x0++].co = s3[i].co;
				}
				i = j;
				break;
			}
		}
	}
	printf("%d", x0);
	for (int i = 0; i < x0; i++)
		printf(" %d %.1f", s3[i].e, s3[i].co);
	//1

	//2
	/*double s[2001];
	for (int i = 0; i < 2001; i++)
		s[i] = 0.0;
	for (int i = 0; i < x; i++)
		s[s3[i].e] += s3[i].co;
	int cnt = 0;
	for (int i = 0; i < 2001; i++)
		if (s[i] != 0.0) cnt++;                        // 判断double类型是否为0不能用!(x)
	printf("%d", cnt);
	for (int i = 2000; i >= 0; i--)
		if (s[i] != 0.0) printf(" %d %.1f", i, s[i]);*/
	//2
}

int main()
{
	int n;

	scanf_s("%d", &k1);
	for (int i = 0; i < k1; i++)
	{
		scanf_s("%d", &s1[i].e);
		scanf_s("%lf", &s1[i].co);   //scanf读取double要用 "%lf" , printf不区分
	}

	scanf_s("%d", &k2);
	for (int i = 0; i < k2; i++)
	{
		scanf_s("%d", &s2[i].e);
		scanf_s("%lf", &s2[i].co);
	}
	product();

	return 0;
}