Codeforces Round #174 (Div. 2)

A题  模拟题   比赛是  sb 了

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
using namespace std;

int main( )
{
    int N,res,k;
    while( scanf("%d",&N) != EOF )
    {
        res = 0;
        for( int i = 1; i < N; i++ )
        {
            bool fell = false; k = 1;
            for( int j = 1; j < N-1; j++ )
            {
                k *= i; k %= N;
                if( k == 1 )
                {
                    fell = true;
                    break;
                }
            }
            if( !fell && k*i%N == 1 )
               res++;
        }
        printf("%d\n",res);
    }
    return 0;
}

B题  模拟题  关键是读懂题目

#include<iostream>
#include<stdio.h>
#include<algorithm>
#include<cstring>
using namespace std;


char str[212345];

int main( )
{
    int N;
    while( scanf("%d",&N) != EOF )
    {
        scanf("%s",&str);
        int len = strlen(str);
        int a = 0,b = 0,c = 0;
        for( int i = 0; i < len; i++ )
        if( str[i] == 'A') a++ ;
        else if( str[i] == 'F')b++;
        else if( str[i] == 'I')c++;
        if( b == len || c >= 2 )
        {
            cout<<0<<endl;
        }
        else 
        if( c != 0 )
             cout<<1<<endl;
        else cout<<a<<endl;
    }
    return 0;
}

C 题 比赛后才想出来  sb了

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
using namespace std;

long long arr[212345],cnt[212345];

int main( )
{
    int N,k,t;
    long long a,b,ans,res;
    scanf("%d",&N);
    memset(cnt,0,sizeof(cnt));
    res = 0; ans = 1;k = 1; arr[1] = 0;
    while( N-- )
    {
        scanf("%d",&t);
        if( t == 1 )
        {
            scanf("%I64d%I64d",&a,&b);
               res += (a*b);
            cnt[a] += b;
            printf("%.6lf\n",double(res*1.0/ans*1.0));
            continue;
        }
        if( t == 2 )
        {
            scanf("%I64d",&arr[++k]);
               res += arr[k];
            ans++;
            printf("%.6lf\n",double(res*1.0/ans*1.0));
            continue;
        }
        if( t == 3 && k >= 2 )
        {
            res = res - arr[k] - cnt[k];
            cnt[k-1] += cnt[k]; cnt[k] = 0;
            ans--;
              k--;
            printf("%.6lf\n",double(res*1.0/ans*1.0));
        }
    }
    return 0;
}

D题  记忆化搜索  关键是 记住三个状态

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
using namespace std;

long long arr[212345];
long long num[212345][3],N,ans,res;

bool  stu[212345][3];
bool  vis[212345][3];

long long DFS( long long x,long long y,int tab )
{
    if( x <= 0 || x > N ) { res = y;  return ans = 0; }
    if(   vis[x][tab]   )
    {
        if( num[x][tab] == -1 )  return res = -1;
               res = num[x][tab] + y;
        return ans = num[x][tab];
    }
    if( stu[x][tab] ){ res = -1;vis[x][tab] = true; num[x][tab] = -1; return -1;}
          stu[x][tab] = true;
    if( !tab )
    {
        long long t = DFS( x-arr[x],y+arr[x],1 );
            vis[x][0] = true;
        if( t != -1 ) ans += arr[x];
        return        num[x][0] = ans;
    }
    else
    {
        long long t = DFS( x+arr[x],y+arr[x],0 );
            vis[x][1] = true;
        if( t != -1 ) ans += arr[x];
        return        num[x][1] = ans;
    }
    return 0;
}

int main( )
{
     int i,x,y;
     scanf("%I64d",&N);
     for( i = 2; i <= N; i++ )
        scanf("%I64d",&arr[i]);
     memset( vis,false,sizeof(vis) );
     memset( stu,false,sizeof(stu) );
     memset( num,0,sizeof(num) );
     for( i = 1; i < N; i++ )
     {
         arr[1] = i; x = 1 + i; y = i;ans = -1; DFS( x,y,0 );
         printf("%I64d\n",res);
     }
    return 0;
}

E题   好题，，，看来N 篇解题报告才出来  还有 一个就是  题目真的很坑啊！  可能是没有读通题目，后来把自己代码换了一个地方就过了；原理没有改变；真是  坑爹的；

#include<iostream>
#include<stdio.h>
#include<cstring>
#include<algorithm>
using namespace std;

const int inf = 1000000007;
int  next[330],pre[330],arr[330],stu[440],h[330],va,wa,k;
int  dp[212345];
int  vis[330],vic[330];
bool fell;

void dfs(int u)
{
    if( pre[u] == 0)
    {
        vis[u] = 2;
        h[u] = 1;
        return;
    }
    if( vis[pre[u]] == 1 )
    {
        fell = false;
        return;
    }
    vis[u] = 1;
    if( vis[pre[u]] == 0 )
        dfs( pre[u] );
    if ( !fell ) return;
    h[u] = h[pre[u]] + 1;
    vis[u] = 2;
}

void DFS( int sta )
{
    if( vic[sta] ) return ;
    va += arr[sta];
    stu[sta] = va;
    vic[sta] = true;
    if(  pre[sta] && next[pre[sta]] == sta )  DFS( pre[sta] );
    return ;
}

int main( )
{
    int N,M,x,y,T;
    while( scanf("%d%d%d",&N,&M,&T) != EOF )
    {
        for( int i = 1; i <= N; i++ )
         scanf("%d",&arr[i]);
        memset( pre,0,sizeof(pre) );
        memset( next,0,sizeof(next) );
        for( int i = 1; i <= M; i++ )
        {
            scanf("%d%d",&x,&y);
            next[y] = x;pre[x] = y;
        }
        fell = true;
        memset( vis,0,sizeof(vis) );
        memset( h,0,sizeof(h));
        for (int i = 1; i <= N; i++)
        if( vis[i] == 0 && fell ) dfs(i);
        if (fell)
        {
            for ( int i = 1; i <= N; i++)
            {
                 T -= ( h[i] - 1) * arr[i];
                if (T < 0) break;
            }
            if (T < 0) fell = false;
        }

        if (!fell)
        {
            printf("0\n");
            continue;
        }
        memset( vic,false,sizeof(vic) );
        for( int i = 1; i <= N; i++ )
        if( next[i] == 0 )
        {
            va = 0; DFS( i );
        }

        memset( dp,0,sizeof(dp) );
        dp[0] = 1;
        for( int i = 1; i <= N; i++ )
        {
            for( int j = stu[i]; j <= T; j++ )
            {
                long long t = (dp[j] + dp[j-stu[i]]);
                if( t >= inf ) t -= inf;
                dp[j] = t;
            }
        }
        printf("%d\n",dp[T]);
    }
    return 0;
}