Project Euler 25 1000-digit Fibonacci number

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题意：在斐波那契数列（ 1 ，1，2，3，5 ...... ）中，第一个有1000位数字的是第几项？

思路：****滚动数组 + 大数加法

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/*************************************************************************
    > File Name: euler025.c
    > Author:    WArobot
    > Blog:      http://www.cnblogs.com/WArobot/
    > Created Time: 2017年06月25日 星期日 11时24分33秒
 ************************************************************************/

#include <stdio.h>
#include <inttypes.h>

int32_t main() {
	int32_t fib[3][1100] = {0};			// fib[][0] 记录该数组所代表数字的最大位数
	fib[1][0] = fib[1][1] = 1;
	fib[2][0] = fib[2][1] = 1;
	int32_t number = 2 , idx1 , idx2 , idx3;
	while( fib[ number % 3 ][0] < 1000 ) {
		number++;
		idx1 = (number - 2) % 3;		// 依靠取模运算进行“滚动”，fib[idx1] < fib[idx2] < fib[idx3]
		idx2 = (number - 1) % 3;
		idx3 = number % 3;
		for(int32_t i = 1 ; i <= fib[idx2][0] ; i++)
			fib[idx3][i] = fib[idx2][i] + fib[idx1][i];
		fib[idx3][0] = fib[idx2][0];
		for(int32_t i = 1 ; i <= fib[idx3][0] ; i++) {
			if( fib[idx3][i] >= 10 ){
				fib[idx3][i+1] += fib[idx3][i] / 10;
				fib[idx3][i] %= 10;
				if( fib[idx3][0] < i + 1 )	fib[idx3][0] = i + 1;
			}
		}
	}
	printf("%d\n",number);
	return 0;
}