UVa 10106 Product

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高精度乘法問題，WA了兩次是因為沒有考慮結果為0的情況。

Product

 

 

The Problem

The problem is to multiply two integers X, Y. (0<=X,Y<10250)

The Input

The input will consist of a set of pairs of lines. Each line in pair contains one multiplyer.

The Output

For each input pair of lines the output line should consist one integer the product.

Sample Input

 

12122222222222222222222222222

 

Sample Output

 

144444444444444444444444444

AC代碼：

 1 //#define LOCAL 2 #include <iostream> 3 #include <cstdio> 4 #include <cstring> 5 using namespace std; 6  7 const int maxn = 265; 8 char a[maxn], b[maxn]; 9 int x[maxn], y[maxn], mul[maxn * 2 + 10];10 void Reverse(char s[], int l);11 12 int main(void)13 {14     #ifdef LOCAL15         freopen("10106in.txt", "r", stdin);16     #endif17 18     while(gets(a))19     {20         gets(b);21         int la = strlen(a);22         int lb = strlen(b);23         memset(mul, 0, sizeof(mul));24         memset(x, 0, sizeof(x));25         memset(y, 0, sizeof(y));26         Reverse(a, la);27         Reverse(b, lb);28         int i, j;29         for(i = 0; i < la; ++i)30             x[i] = a[i] - ‘0‘;31         for(i = 0; i < lb; ++i)32             y[i] = b[i] - ‘0‘;33 34         for(i = 0; i < lb; ++i)35         {36             int s = 0, c = 0;37             for(j = 0; j < maxn; ++j)38             {39                 s = y[i] * x[j] + c + mul[i + j];40                 mul[i + j] = s % 10;41                 c = s / 10;42             }43         }44 45         for(i = maxn * 2 + 9; i >= 0; --i)46             if(mul[i] != 0)47                 break;48         if(i < 0)49             cout << 0;50         else51         {52             for(; i >=0; --i)53                 cout << mul[i];54         }55         cout << endl;56     }57     return 0;58 }59 //用來反轉數組60 void Reverse(char s[], int l)61 {62     int i;63     char t;64     for(i = 0; i < l / 2; ++i)65     {66         t = s[i];67         s[i] = s[l - i -1];68         s[l - i -1] = t;69     }70 }

代碼君