2016"百度之星" - 资格赛（Astar Round1）Problem B

B

题解

推下前几个，发现这是一个斐波那契数列。
高精度。

#include <iostream>#include <cstdio>#include <string>#include <algorithm>using namespace std;typedef unsigned long long ull;const int maxn = 210;string   dp[maxn];string add(string &a, string& b){    string ans;    string aa(a.rbegin(), a.rend());    string bb(b.rbegin(), b.rend());    int i = 0;    int carry = 0, sum = 0;    while(i < aa.length() && i < bb.length()){        sum = (aa[i] - '0') + (bb[i] - '0') + carry;        carry = sum / 10;        ans.push_back(sum % 10 + '0');        ++i;    }    while(i < aa.length()){        sum = (aa[i] - '0') + carry;        carry = sum / 10;        ans.push_back(sum % 10 + '0');        ++i;    }    while(i < bb.length()){        sum = (bb[i] - '0') + carry;        carry = sum / 10;        ans.push_back(sum % 10 + '0');        ++i;    }    if(carry){        ans.push_back(carry + '0');    }    return string(ans.rbegin(), ans.rend());}int main(){    dp[1] = "1", dp[2] = "2";    for(int i = 3; i <= 200; ++i){        dp[i] = add(dp[i - 1], dp[i - 2]);    }    int n;    while(cin >> n){        cout << dp[n] << endl;    }    return 0;}