唔,bign类高精度还是蛮好用的。
#include <iostream> #include <cstdlib> #include <cstdio> #include <cstring> #include <string> using namespace std; const int MAXN = 2010; int n; struct bign { int len, s[MAXN]; bign () { memset(s, 0, sizeof(s)); len = 1; } bign (int num) {*this = num;} bign (const char *num) { *this = num;} bign operator = (const char *num) { len = strlen(num); for(int i = 0; i < len; i++) s[i] = num[len-i-1] - '0'; return *this; } bign operator = (int num) { char s[MAXN]; sprintf(s, "%d", num); *this = s; return *this; } bign operator +(const bign &b) const { bign c; c.len = 0; for(int i = 0, g = 0; g || i < max(len, b.len); i++) { int x = g; if(i < len) x += s[i]; if(i < b.len) x += b.s[i]; c.s[c.len++] = x%10; g = x / 10; } return c; } bool operator < (const bign &b) const { if(len != b.len) return len < b.len; for(int i = len-1; i >= 0; i--) { if(s[i] != b.s[i]) return s[i] < b.s[i]; } return false; } void print() { for(int i = len-1; i >= 0; i--) { printf("%d", s[i]); } printf("\n"); } }; void solve() { if(n == 1) { printf("1\n"); return ;} if(n == 2) { printf("1\n"); return ;} if(n == 3) { printf("1\n"); return ;} if(n == 4) { printf("1\n"); return ;} bign f1 = 1, f2 = 1, f3 = 1, f4 = 1, f5 = 1; for(int i = 5; i <= n; i++) { f5 = f1+f2+f3+f4; f1 = f2; f2 = f3; f3 = f4; f4 = f5; } f5.print(); } int main() { while(~scanf("%d", &n)) { solve(); } return 0; }