PAT甲级练习题A1002. A+B for Polynomials
2016-07-17 20:52
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题目描述
This time, you are supposed to find A+B where A and B are two polynomials.Input
Each input file contains one test case. Each case occupies 2 lines, and each line contains the information of a polynomial: K N1 aN1 N2 aN2 … NK aNK, where K is the number of nonzero terms in the polynomial, Ni and aNi (i=1, 2, …, K) are the exponents and coefficients, respectively. It is given that 1 <= K <= 10,0 <= NK < … < N2 < N1 <=1000.
Output
For each test case you should output the sum of A and B in one line, with the same format as the input. Notice that there must be NO extra space at the end of each line. Please be accurate to 1 decimal place.
Sample Input
2 1 2.4 0 3.2
2 2 1.5 1 0.5
Sample Output
3 2 1.5 1 2.9 0 3.2
题目解析
第一种我使用两个链表储存两个多项式,编程过程中出现两个问题,一个是输出的格式不对;另外一个是在循环中continue使用的不对,导致错误的跳过了循环体中后面的过程,这个找了一个晚上才发现,一直有两个过不了。第二种是使用了数组的下标代表次数,因为次数小于1000,所以可以直接用简单的方法。而且只要一个数组就OK了。所以做题目的时候要注意条件,选择合适的简单的方法解决问题。
代码
第一种
//错误的continue if ( N1==N2 ) { ++i, ++j; if (an1 + an2 < 0.1) { continue; } element ele(N1, an1 + an2); out.push_back(ele); }
改正后
#include<iostream> #include<vector> #include<cmath> using namespace std; class element { public: int expo; double coeff; element(int ex = 0, double co = 0) :expo(ex), coeff(co) {}; }; int main() { int K, N; double an; vector<vector<element> > poly(2); vector<element> out; for (int i = 0; i < 2; ++i) { cin >> K; for (int j = 0; j < K; ++j) { cin >> N >> an; element ele(N, an); poly[i].push_back(ele); } } for (int i = 0, j = 0; i < poly[0].size() && j < poly[1].size();) { int N1 = poly[0][i].expo, N2 = poly[1][j].expo; double an1 = poly[0][i].coeff, an2 = poly[1][j].coeff; //原来的错误在这里 if ( N1==N2 ) { ++i, ++j; if (an1 + an2 != 0) //这里我觉得可以考虑下浮点数的边界问题,不过通过了 { element ele(N1, an1 + an2); out.push_back(ele); } } else if (N1 > N2) { element ele(N1, an1); out.push_back(ele); ++i; } else { element ele(N2, an2); out.push_back(ele); ++j; } if (i == poly[0].size()) { for (int k = j; j < poly[1].size(); ++j) { out.push_back(poly[1][j]); } } else if (j == poly[1].size()) { for (int k = i; i < poly[0].size(); ++i) { out.push_back(poly[0][i]); } } } cout << out.size(); for (int i = 0; i < out.size(); ++i) { printf(" %d %.1f",out[i].expo,out[i].coeff); } cout << endl; system("pause"); return 0; }
第二种
#include<iostream> #include<vector> using namespace std; int maxexp = 1001; vector<double> poly(maxexp, 0); int main() { int K, N; double an; int i = 2; while (i--) { cin >> K; while (K--) { cin >> N >> an; poly += an; } } int cnt = 0; for (int i = maxexp - 1; i >= 0; --i) { if (poly[i] != 0) { ++cnt; } } cout << cnt; if (cnt != 0) { for (int i = maxexp - 1; i >= 0; --i) { if (poly[i] != 0) { printf(" %d %.1f", i, poly[i]); } } } cout << endl; system("pause"); return 0; }
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