Bzoj1754: [usaco 2005 Qua] Bull math

1754: [usaco 2005 Qua] Bull mathtime limit: 5 sec memory limit: 64 MB
Submit: 374 solved: 227
[Submit] [Status] Descriptionbulls are so much better at math than the cows. they can multiplyhuge integers together and get perfectly precise answers... or sothey say. farmer John wonders if their answers are correct. helphim check the Bulls 'answers. read in two positive integers (nomore than 40 digits each) and compute their product. output it asa normal number (with no extra leading zeros ). FJ asks that you do this yourself; don't use a special libraryfunction for the multiplication. input two numbers and output their product input * lines 1 .. 2: Each line contains a single decimal number. output * Line 1: The exact product of the two input linessample input11111111111111
1111111111

Sample output12345679011110987654321hintsource

Gold

Question:

Ha ha, the Gold Group has such a problem, explosion proof zero it...

Code:

 1 #include<cstdio> 2  3 #include<cstdlib> 4  5 #include<cmath> 6  7 #include<cstring> 8  9 #include<algorithm>10 11 #include<iostream>12 13 #include<vector>14 15 #include<map>16 17 #include<set>18 19 #include<queue>20 21 #include<string>22 23 #define inf 100000000024 25 #define maxn 1000026 27 #define maxm 500+10028 29 #define eps 1e-1030 31 #define ll long long32 33 #define pa pair<int,int>34 35 #define for0(i,n) for(int i=0;i<=(n);i++)36 37 #define for1(i,n) for(int i=1;i<=(n);i++)38 39 #define for2(i,x,y) for(int i=(x);i<=(y);i++)40 41 #define for3(i,x,y) for(int i=(x);i>=(y);i--)42 43 #define mod 100000000744 45 using namespace std;46 47 inline int read()48 49 {50 51     int x=0,f=1;char ch=getchar();52 53     while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}54 55     while(ch>=‘0‘&&ch<=‘9‘){x=10*x+ch-‘0‘;ch=getchar();}56 57     return x*f;58 59 }60 int n,m,a[maxn],b[maxn],c[maxn];61 char ch;62 63 int main()64 65 {66 67     freopen("input.txt","r",stdin);68 69     freopen("output.txt","w",stdout);70 71     ch=getchar();72     while(ch<=‘9‘&&ch>=‘0‘)a[++n]=ch-‘0‘,ch=getchar();73     for1(i,n>>1)swap(a[i],a[n+1-i]);74     ch=getchar();75     while(ch<=‘9‘&&ch>=‘0‘)b[++m]=ch-‘0‘,ch=getchar();76     for1(i,m>>1)swap(b[i],b[m+1-i]);77     for1(i,n)78      for1(j,m)79       c[i+j-1]+=a[i]*b[j];80     for1(i,n+m)c[i+1]+=c[i]/10,c[i]%=10;81     int t=n+m;82     while(!c[t])t--;83     for3(i,t,1)printf("%d",c[i]);84     printf("\n");85 86     return 0;87 88 }

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Bzoj1754: [usaco 2005 Qua] Bull math