第五章-算法入门

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5.1 equation
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#include<iostream>  #include<stdio.h>  #include<string>  using namespace std;  double calcul(double x)  {      return 8*x*x*x*x + 7*x*x*x + 2*x*x +3*x + 6;  }  int main()  {      double y;      cin >> y;      if(y < 6 || y > calcul(100))      {          cout << "No solution!" <<endl;      }      else          {           double x;          double left = 0;          double right = 100;          x = (left + right) / 2;          while(calcul(x) != y || (right - left) > 1e-8)          {              if(calcul(x) == y || (right - left) < 1e-8)              {                  printf("%.4lf",x);                  return 0;              }              else if(calcul(x) > y)              {                  right = x;              }              else if(calcul(x) < y)              {                  left = x;              }              x = (left + right) / 2;          }      printf("%.4lf\n",x);      }      return 0;  }

5.2 sequences
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（使用64位整型）

#include<iostream>  #include<stdio.h>  #include<string>  using namespace std;  int main()  {      __int64 a1,a2,a3;      int k;      scanf("%I64d %I64d %I64d %d",&a1,&a2,&a3,&k);      a1 = a1;      a2 = a2;      a3 = a3;      __int64 d,q1,q2;      d = a2 - a1;      if(d == (a3-a2))      {          cout << "arithmetic sequences. "<<endl;          printf("%I64d\n",(a1 + (k-1) * d) % 1000000007);          return 0;      }      __int64 q = a2 / a1;      k--;      cout << "geometric sequences. " << endl;      //快速幂      __int64 res = a1;      while(k>0)      {          if(k&1)              res = (res*q)% 1000000007;          q = (q*q) % 1000000007;          k>>=1;       }       printf("%I64d\n",res % 1000000007);      return 0;  }

5.3 Game_Prediction
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#include<iostream>    #include<stdio.h>    #include<string>    using namespace std;    bool arr[10086];    int main()    {        int count = 0;      int m,n;        cin >> m >> n;        int a;        int i;        for(i =0; i < n ;i++)        {            cin >> a;            arr[a] = true;        }        int max = m * n;        while(arr[max])        {            count++;            max--;        }        //max为对方最大牌         i = 1;        while(arr[i])        {            i++;        }        //i为对方最小牌         while(!arr[i])        {            i++;        }         //i为我方有效最小牌         int neg = 0; //相连0的数量         int pos = 0; //相连1的数量         for(int j = max; j >= i; j--)        {            while(!arr[j])            {              neg++;               j--;          }          while(arr[j])              {              pos++;                   j--;          }          if(neg >= pos)           {              neg -= pos;              pos = 0;          }          else           {              count += neg;              pos -= neg;              neg = 0;          }      }        cout << count <<endl;        return 0;    }

5.4 Painter
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#include<iostream>  #include<stdio.h>  #include<string>  #include<algorithm>  using namespace std;  double arr[15];  double minu[15];  int main()  {      int i,j;      int n;      cin >> n;      for(i = 1; i <= n;i++)          cin >> arr[i];      cin >> arr[0]; //0为需要的灰色颜料      double ml = 0;      bool flag = false;      bool flag2= true;      double count = 0;      for(i = 1; i<= 40; i++)      {          if(flag) break;          ml = i*50; //买到颜料体积           flag2 = true;          for(j = 1; j <= n; j++)          {              if(arr[j] > ml) //需要超过买到               {                  flag2 = false;                  break;              }              else                  minu[j] = ml - arr[j];          }          count = 0;          while(flag2)          {              sort(minu+1,minu+n+1);              if(!minu[n-2]) break;              count++;              if(count >= arr[0])              {                  flag = true;                  break;              }                         minu[n]--;              minu[n-1]--;              minu[n-2]--;          /// cout <<minu[12]<<" "<<minu[11]<<" "<<minu[10]<<endl;          }      }      cout << i-1;       return 0;  }

5.5 Best_Cow_Line
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#include<iostream>  #include<stdio.h>  #include<string>  #include<algorithm>  using namespace std;  int main()  {      int n;      cin >> n;      string s;      cin >> s;      int left = 0;      int right = n-1;      bool flag;      while(left <= right)      {          flag = false;           //确定left与right较小的一个，相同时比较下一位          for(int i = 0; i+left < right; i++)          {              if(s[i+left] < s[right-i])               {                  flag = true;                  break;              }              else if(s[i+left] > s[right-i])              {                  flag = false;                  break;              }          }          if(flag)          {              cout << s[left];              left++;          }          else          {              cout << s[right];              right--;          }      }         return 0;  }

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