joj1277

1277: Fibonacci Freeze

Result	TIME Limit	MEMORY Limit	Run Times	AC Times	JUDGE
	3s	8192K	2367	561	Standard

The Fibonacci numbers (0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, ...) are defined by the recurrence:



Write a program to calculate the Fibonacci Numbers.

Input and Output

The input to your program would be a sequence of numbers smaller or equal than 500, each on a separate line, specifying which Fibonacci number to calculate.

Your program should output the Fibonacci number for each input value, one per line.

Sample Input

5
7
11

Sample Output

The Fibonacci number for 5 is 5
The Fibonacci number for 7 is 13
The Fibonacci number for 11 is 89

This problem is used for contest: 111

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由于要求500项斐波那契数列，用到大数加法。直接在递推写斐波那契数列的程序中将其中的加法替换。

#include <stdio.h>
#include <string.h>

void add(char *a, char *b, char *c)
{
int i, j, i1, i2, tmp, carry;

int len1 = strlen(a);
int len2 = strlen(b);
char ch;

i1 = len1-1;
i2 = len2-1;
j = carry = 0;

for ( ; i1>=0 && i2>=0; --i1, --i2, ++j)
{
tmp = a[i1]-'0'+b[i2]-'0'+carry;
carry = tmp / 10;
c[j] = tmp % 10 + '0';
}

while (i1 >= 0)
{
tmp = a[i1--] - '0' + carry;
carry = tmp / 10;
c[j++] = tmp % 10 + '0';
}
while (i2 >= 0)
{
tmp = b[i2--] - '0' + carry;
carry = tmp / 10;
c[j++] = tmp % 10 + '0';
}

if (carry != 0)
{
c[j++] = carry + '0';
}
c[j] = '\0';
for (i=0, --j; i<j; ++i, --j)
{
ch = c[i];
c[i] = c[j];
c[j] = ch;
}
a[i1] = '\0';
b[i2] = '\0';
}

int main(void)
{
int val;

char a[1000], b[1000], c[1000];

while (scanf("%d", &val) == 1)
{
a[0] = '0';
a[1] = '\0';
b[0] = '1';
b[1] = '\0';

if (0 == val)
{
c[0] = '0';
c[1] = '\0';
}
else if (1 == val)
{
c[0] = '1';
c[1] = '\0';
}
else
{
for (int i=2; i<=val; i++)
{
add(a, b, c);
strcpy(a, b);
strcpy(b, c);
}
}

printf("The Fibonacci number for %d is %s\n", val, c);
}

return 0;
}