爬楼梯 （大数加法）

 1 #include <iostream>
 2 #include <vector>
 3 #include <string>
 4 using namespace std;
 5 string add(string s1, string s2) {
 6     int len1 = s1.length(), len2 = s2.length();
 7     int maxlen = max(len1, len2) + 1;
 8     string res(maxlen, ‘0‘);
 9     int flag = 0;
10     int i = len1 - 1, j = len2 - 1, k = maxlen - 1;
11     for (; i >= 0 && j >= 0; i--, j--) {
12         int temp = (s1[i] - ‘0‘) + (s2[j] - ‘0‘) + flag;
13         flag = temp / 10;
14         res[k--]= temp % 10 + ‘0‘;
15     }
16     while (i >= 0) {
17         int temp = s1[i--] - ‘0‘ + flag;
18         flag = temp / 10;
19         res[k--] = temp % 10 + ‘0‘;
20     }
21     while (j >= 0) {
22         int temp = s2[j--] - ‘0‘ + flag;
23         flag = temp / 10;
24         res[k--] = temp % 10 + ‘0‘;
25     }
26     res[k] = flag + ‘0‘;
27     if (flag) {
28         return res;
29     } else {
30         return res.substr(1);
31     }
32 }
33 string jumpFloor(int number) {
34     vector<string> dp(number + 1, "1");
35     for (int i = 2; i <= number; i++) {
36         dp[i] = add(dp[i - 1], dp[i - 2]);
37     }
38     return dp[number];
39 }
40 
41 int main() {
42     int n;
43     cin >> n; 
44     cout << jumpFloor(n) << endl;
45 }