[usaco] Chapter1-Getting started(Section 1.5)

 

/*
ID: bbezxcy1
PROG: numtri
LANG: C++
*/
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int n,map[1002][1002];
int main(){
	int n,i,j,a,b,c;
    freopen("numtri.in","r",stdin );
    freopen("numtri.out","w",stdout );
	while(scanf("%d",&n)!=EOF){
		for(i=1;i<=n;i++){
			for(j=1;j<=i;j++){
				scanf("%d",&map[i][j]);
			}
		}
		for(i=n-1;i>=1;i--){
			for(j=1;j<=i;j++){
				map[i][j]+=max(map[i+1][j],map[i+1][j+1]);
			}
		}
		printf("%d\n",map[1][1]);
	}
	return 0;
}

 

//第二题，只把打表代码写上吧

#include<iostream>
#include<cstring>
#include<cstdio>
#include<cmath>
using namespace std;
bool   isPrim(int  n){
    int   m=sqrt(n);
	if(n==2)return 1;
    for(int   i=2;i <=m;i++){
        if(n%i==0)
        return   false;
    }
    return   true;
}

bool isback(int n){
    char str[20];
    int len=0;
    while(n)
    {
		str[len++]=n%10;
		n/=10;
    }
	for(int i=0;i<len;i++){
        if(str[i]!=str[len-i-1]){
			return 0;
		}
	}
	return 1;
}
int main(){
    int cnt=1;
    freopen("namenum.out","w",stdout );
    cout<<2<<" ";
	for(int i=2;i<=100000000;i++){
	    if(i%2==0)continue;
		if(isPrim(i)&&isback(i)){
		    cnt++;
			printf("%d,",i);
		}
	}
	cout<<"cnt="<<cnt<<endl;
    return 0;
}

  /*

ID: bbezxcy1
PROG: sprime
LANG: C++
*/
#include<iostream>
#include<cstring>
#include<cmath>
#include<cstdio>
using namespace std;
int len;
bool check(int d)
{
     int i;
     for (i=2;i<=(int)sqrt(d);i++)
        if (d%i==0) return true;
     return false;
}
int tail[5];//={1,3,7,9};
void dfs(int num,int dep)
{
    if(dep==len)
    {
        printf("%d\n",num);
        return;
    }
    int a,i;
    for(i=0;i<4;i++)
    {
        a=num*10+tail[i];
        if(check(a))
        {
            dfs(a,dep+1);
        }
    }
}
int main()
{
    freopen("sprime.in","r",stdin );
    freopen("sprime.out","w",stdout );
    tail[0]=1;tail[1]=3;tail[2]=7;tail[3]=9;
    while(scanf("%d",&len)!=EOF)
    {
        if(len==1){
            printf("2\n3\n5\n7");
            continue;
        }
        dfs(2,1);
        dfs(3,1);
        dfs(5,1);
        dfs(7,1);
    }
    return 0;
}

  /*

ID: bbezxcy1
PROG: checker
LANG: C++
*/
#include<fstream>
#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int aaa[50],bbb[50],ccc[50],n,res[50],tot;
ifstream fin("checker.in");
ofstream fout("checker.out");
void dfs(int dep)  //dep代表当前的行
{
    int i;
    if(dep==n)
    {
        tot++;
        if(tot<=3)
        {
            for(i=0;i<n-1;i++)
            {
                fout<<res[i]+1<<" ";
                //printf("%d ",res[i]+1);
            }//printf("%d\n",res[n-1]+1);
            fout<<res[n-1]+1<<endl;
        }
        return;
    }
    for(i=0;i<n;i++)
    {
        if(!aaa[i]&&!bbb[dep-i+n]&&!ccc[i+dep])
        {
            aaa[i]=bbb[dep-i+n]=ccc[i+dep]=1;
            res[dep]=i;
            dfs(dep+1);
            aaa[i]=bbb[dep-i+n]=ccc[i+dep]=0;
        }
    }
}

int main()
{
//    freopen("checker.in","r",stdin );
//    freopen("checker.out","w",stdout );
    int i,j,a,b,c;
    while(fin>>n)//scanf("%d",&n)!=EOF
    {
        tot=0;
        memset(aaa,0,sizeof(aaa));
        memset(bbb,0,sizeof(bbb));
        memset(ccc,0,sizeof(ccc));
        dfs(0);
        fout<<tot<<endl;
        //printf("%d\n",tot);
    }
    return 0;
}