HDU 2046

思路：找递推关系a[n] = a[n-1]+a[n-2].

#include<stdio.h>long long int a[51];int main(){    int i,n;    a[1] = 1;    a[2] = 2;    a[3] = 3;    for(i = 3;i <= 50;i ++)        a[i] = a[i-2]+a[i-1];    while(~scanf("%d",&n))        printf("%I64d\n",a[n]);    return 0;}