504. Base 7

Problem:

Given an integer, return its base 7 string representation.

Example 1:

Input: 100
Output: "202"

Example 2:

Input: -7
Output: "-10"

Note: The input will be in range of [-1e7, 1e7].

思路：

Solution (C++):

string convertToBase7(int num) {
    if (num == 0)  return "0";
    string res = "";
    int x = abs(num);
    
    while (x) {
        res = to_string(x%7) + res;
        x /= 7;
    }
    return (num > 0 ? "" : "-") + res;
}

性能：

Runtime: 0 ms  Memory Usage: 6 MB

思路：

Solution (C++):

int fib(int N) {
    if (N == 0)  return 0;
    vector<int> dp(N+1, 0);
    dp[1] = 1;
    for (int i = 2; i <= N; ++i) {
        dp[i] = dp[i-1] + dp[i-2];
    }
    return dp[N];
}

性能：

Runtime: 0 ms  Memory Usage: 6.2 MB