題意:由紅白藍按照規則形成的旗幟的種類數
WA點:注意longl long
則f[i] = f[i-1] + f[i -2] ,因爲,在f[i-1]後面加一種顏色(紅或白)或者在f[i-2]中加上包括藍的兩種顏色即可形成f[i];
#include <stdio.h>
long long color[46];
int main (){
int n;
color[1] = 2;
color[2] = 2;
color[3] = 4;
color[4] = 6;
for (int i = 5; i <= 45; i ++)
color[i] = color[i - 1] + color[i - 2];
while(scanf("%d", &n) != EOF)
printf("%lld\n", color[n]);
return 0;
}