很久不做算法题，模拟考一团糟，今天自己实现记录下：
1.生成N位格雷码，e.g.[00,01,10,11]
1 #include <iostream> 2 #include <string> 3 #include <cmath> 4 using namespace std; 5 6 7 const int n = 4; 8 int size = 0; 9 int num = int(pow(2, n)); 10 string* codes = new string[num]; 11 bool push(string* arr, string target){ 12 for (int i = 0; i < size; i++){ 13 if (target == arr[i]) return false; 14 } 15 arr[size] = target; 16 size++; 17 return true; 18 } 19 void make(string last){ 20 if (size == num) return; 21 int pos = last.length() - 1; 22 bool flag = false; 23 string copy; 24 while (flag == false){ 25 copy = last; 26 if (copy[pos] == '1'){ 27 copy[pos] = '0'; 28 } 29 else if (copy[pos] == '0'){ 30 copy[pos] = '1'; 31 } 32 pos = ((pos--) + last.length()) % last.length(); 33 flag = push(codes, copy); 34 } 35 last = copy; 36 make(last); 37 } 38 39 int main(){ 40 string str(n,'0'); 41 push(codes, str); 42 make(str); 43 for (int i = 0; i < num;i++) 44 cout << codes[i]<<endl; 45 system("pause"); 46 return 0; 47 }
2.两个不大于1000位的大整数乘法：
1 #include <iostream> 2 #include <string> 3 #define NUM(alp) (alp-'0') 4 #define CHAR(num) (num+'0') 5 using namespace std; 6 7 int** writeMatrix(string num1,string num2){ 8 int** matrix = new int*[num2.length()]; 9 for (int i = 0; i < num2.length(); i++){ 10 matrix[i] = new int[num1.length()]; 11 memset(matrix[i], 0, num1.length()); 12 } 13 int carry = 0,left=0; 14 for (int i = num2.length() - 1; i >= 0; i--){ 15 for (int j = num1.length() - 1; j >= 0; j--){ 16 //cout << " i: " << num2.length() - i - 1 << " j: " << num1.length() << " i*j: " << NUM(num2[i])*NUM(num1[j]); 17 matrix[-i+num2.length() - 1][j] = NUM(num2[i])*NUM(num1[j]); 18 } 19 } 20 return matrix; 21 } 22 string calcuMatrix(int** matrix,int row,int col){ 23 int carry = 0, left = 0, sum = 0; 24 string res=""; 25 for (int i = 0, j = col - 1; j >= 0; j--){ 26 sum = 0; 27 for (int m = i, n = j; m <= (row - 1) && n <= (col - 1); m++, n++){ 28 sum += matrix[m][n]; 29 } 30 left = (sum + carry) % 10 ; 31 carry = sum / 10; 32 res += CHAR(left); 33 } 34 for (int i = 1, j = 0; i < row; i++){ 35 sum = 0; 36 for (int m = i, n = j; m <= (row - 1) && n <= (col - 1); m++, n++){ 37 sum += matrix[m][n]; 38 } 39 left = (sum + carry) % 10 ; 40 carry = sum / 10; 41 res += CHAR(left); 42 } 43 if (carry > 0){ 44 while (carry % 10 != 0){ 45 res += CHAR(carry % 10); 46 carry /= 10; 47 } 48 } 49 return res; 50 } 51 string reverse(string str){ 52 char ch; 53 for (int i = str.length() - 1,j=0; i >= (str.length()-1)/2; i--,j++){ 54 ch = str[i]; 55 str[i] = str[j]; 56 str[j] = ch; 57 } 58 return str; 59 } 60 int main(){ 61 string num1, num2; 62 string res; 63 cin >> num1; 64 cin >> num2; 65 int row = num2.length(),col=num1.length(); 66 cout << reverse(calcuMatrix(writeMatrix(num1, num2), row, col)); 67 system("pause"); 68 return 0; 69 }
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