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sopherwang/gist:5101a962f04666b21ee1

Created September 14, 2014 21:52
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  1. sopherwang created this gist Sep 14, 2014.
    30 changes: 30 additions & 0 deletions gistfile1.java
    View file
    Original file line number Diff line number Diff line change
    @@ -0,0 +1,30 @@
    public int climbStairsDP(int n)
    {
    //dp
    //dp[i]: how many ways to reach i.(i < n)
    if (n <= 1)
    {
    return n;
    }
    int[] dp = new int[n + 1];
    dp[0] = 1;
    dp[1] = 1;
    for (int i = 2; i <= n; i++)
    {
    dp[i] = dp[i - 1] + dp[i - 2];
    }
    return dp[n];
    }

    public int climbStairs(int n)
    {
    // Note: The Solution object is instantiated only once and is reused by each test case.
    int p = 1, q = 1;
    for (int i = 2; i <= n; i++)
    {
    int temp = q;
    q += p;
    p = temp;
    }
    return q;
    }