《3820: Revenge of Fibonacci 》

一开始想的是java大数然后字典树插入前40个。

但是这样会爆内存，数太大了。

但其实超过40之后保存前50位就可以了，这样精度也能保证。

这题题目内存很紧，优化了好几次常数终于过了。

#include<bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef pair<int,int> pii;
const int N = 1e6 + 5;
const int M = 4e4+5;
const LL Mod = 1e9+7;
#define pi acos(-1)
#define INF 1e9
#define CT0 cin.tie(0),cout.tie(0)
#define IO ios::sync_with_stdio(false)
#define dbg(ax) cout << "now this num is " << ax << endl;
namespace FASTIO{
    inline LL read(){
        LL x = 0,f = 1;char c = getchar();
        while(c < '0' || c > '9'){if(c == '-') f = -1;c = getchar();}
        while(c >= '0' && c <= '9'){x = (x<<1)+(x<<3)+(c^48);c = getchar();}
        return x*f;
    }
}
using namespace FASTIO;

int tree[N * 5][10],tim[N * 10],k = 0;
char a[55],b[55],c[55],s[55];
void Insert(char s[],int id){
    int len = strlen(s),p = 0;
    for(int i = 0;i < len;++i){
        int c = s[i] - '0';
        if(tree[p][c] == 0) {
            tree[p][c] = ++k;
            tim[tree[p][c]] = id;
        }
        p = tree[p][c];
    }
}
int query(char s[]){
    int len = strlen(s),p = 0;
    for(int i = 0;i < len;++i){
        int c = s[i] - '0';
        if(tree[p][c] == 0) return -1;
        p = tree[p][c];
    }
    return tim[p];
}
void Add(int up) {
    int la = strlen(a) - 1,lb = strlen(b) - 1,res[105],l = 0,t = 0;
    while(la >= 0){
        res[l] = (a[la] - 48) + (b[lb] - 48) + t;
        t = 0;
        if(res[l] >= 10)res[l] -= 10,t = 1;
        la--,lb--,l++;
    }
    while(lb >= 0){
        res[l] = b[lb] - 48 + t;
        t = 0;
        if(res[l] >= 10) res[l] -= 10,t = 1;
        lb--,l++;
    }
    if(t) res[l++] = 1;
    int i = 0,k = 0;
    if(l > up) k = l - up;
    l--;
    while(l >= 0 && i < up) c[i++] = res[l--] + 48;
    c[i] = '';
    //计算完c的值。即a + b
    lb = strlen(b);
    int lc = strlen(c);
    for(int j = 0;j < lb - k;j++) a[j] = b[j];//轮换，a = b
    a[lb-k] = '';
    for(int j = 0;j < lc;j++) b[j] = c[j];//b = c;
    b[lc] = '';
}
void init()
{
    a[0] = '1',a[1] = '';
    b[0] = '1',b[1] = '';
    Insert(a,0);Insert(b,1);
    for(int i = 2;i < 100000;++i){
        Add(50);
        Insert(c,i);
    }
}
int main()
{
    init();
    int ca;ca = read();
    int tot = 0;
    while(ca--)
    {
        scanf("%s",s);
        int ans = query(s);
        printf("Case #%d: %d
",++tot,ans);
    }
    system("pause");
    return 0;
}