poj2506 dp

dp[i]=dp[i-2]*2+dp[i-1];

//poj2506 #include <iostream> #include <algorithm> using namespace std; struct numtype { int len,a[1000]; }dp[252]; int n; void add(numtype a, numtype b, numtype &c) { int i,len=max(a.len,b.len); for (i=1;i<=len;i++) c.a[i]=a.a[i]+b.a[i]; for (i=1;i<=len;i++) if (c.a[i]>9) { c.a[i]-=10; c.a[i+1]++; } if (c.a[len+1]!=0) c.len=len+1; else c.len=len; } void cheng2(numtype &x) { int i; for (i=1;i<=x.len;i++) x.a[i]*=2; for (i=1;i<=x.len;i++) if (x.a[i]>9) { x.a[i]-=10; x.a[i+1]++; } if (x.a[x.len+1]!=0) x.len++; } int main() { int i; while (cin >> n) { memset(dp,0,sizeof(dp)); dp[0].len=1; dp[0].a[1]=1; dp[1].len=1; dp[1].a[1]=1; for (i=2;i<=n;i++) { cheng2(dp[i-2]); add(dp[i-2],dp[i-1],dp[i]); } for (i=dp[n].len;i>=1;i--) cout << dp[n].a[i]; cout << endl; } //system("pause"); return 0; }