URAL 1133. Fibonacci Sequence

题目链接

 1 #include <cstdio>

 2 #include <string>

 3 #include <cstring>

 4 #include <iostream>

 5 using namespace std;

 6 #define LL long long

 7 #define INF 2000000000

 8 LL p[3001];

 9 int main()

10 {

11     int i;

12     LL a,fa,fb,b,n;

13     LL str,mid,end;

14     cin>>a>>fa>>b>>fb>>n;

15     if(a > b)

16     {

17         swap(a,b);

18         swap(fa,fb);

19     }

20     str = -INF;

21     end = INF;

22     while(str <= end)

23     {

24         mid = (str+end)/2;

25         int f1,f2;

26         f1 = f2 = 0;

27         memset(p,-1,sizeof(p));

28         p[a+1000] = fa;

29         p[a+1+1000] = mid;

30         for(i = a+2;i <= b;i ++)

31         {

32             p[i+1000] = p[i-1+1000] + p[i-2+1000];

33             if(p[i+1000] > INF)

34             {

35                 f1 = 1;

36                 break;

37             }

38             if(p[i+1000] < -INF)

39             {

40                 f2 = 1;

41                 break;

42             }

43         }

44         if(f1)

45         end = mid - 1;

46         else if(f2)

47         str = mid + 1;

48         else if(p[b+1000] == fb)

49         break;

50         else if(p[b+1000] > fb)

51         end = mid - 1;

52         else if(p[b+1000] < fb)

53         str = mid + 1;

54     }

55     if(n <= b&&n >= a)

56     ;

57     else if(n < a)

58     {

59         p[a+1000] = fa;

60         p[a+1+1000] = mid;

61         for(i = a-1;i >= n;i --)

62         {

63             p[i+1000] = p[i+2+1000] + p[i+1+1000];

64         }

65     }

66     else

67     {

68         p[a+1000] = fa;

69         p[a+1+1000] = mid;

70         for(i = a+2;i <= n;i ++)

71         {

72             p[i+1000] = p[i-1+1000] + p[i-2+1000];

73         }

74     }

75     cout<<p[n+1000]<<endl;

76     return 0;

77 }