在用Python刷LeedCode面试题49丑数时 IndexError: list assignment index out of range怎么解决

在用Python刷LeedCode面试题49丑数时，遇到IndexError: list assignment index out of range 错误，下面介绍怎么解决。

class Solution:
    def nthUglyNumber(self, n: int) -> int:
        p2,p3,p5 = 0,0,0
        dp = [1，]
        i=1
        while i!=n:
            dp[i] = min(dp[p2] * 2,dp[p3] * 3,dp[p5] * 5)
            if dp[i] == dp[p2] * 2: p2 += 1
            if dp[i] == dp[p3] * 3: p3 += 1
            if dp[i] == dp[p5] * 5: p5 += 1
            i += 1
        return dp[n-1]

出现IndexError: list assignment index out of range错误，原因是空数组不能直接指定位置。解决：‘
方法一，指定列表的长度：

class Solution:
    def nthUglyNumber(self, n: int) -> int:
        p2,p3,p5 = 0,0,0
        dp = [0]*n
        dp[0] = 1
        i=1
        while i!=n:
            dp[i] = min(dp[p2] * 2,dp[p3] * 3,dp[p5] * 5)
            if dp[i] == dp[p2] * 2: p2 += 1
            if dp[i] == dp[p3] * 3: p3 += 1
            if dp[i] == dp[p5] * 5: p5 += 1
            i += 1
        return dp[n-1]

方法二，用append()：

class Solution:
    def nthUglyNumber(self, n: int) -> int:
        p2,p3,p5 = 0,0,0
        dp = [1，]
        i=1
        while i!=n:
            value = min(dp[p2] * 2,dp[p3] * 3,dp[p5] * 5)
            dp.append(value)
            if value == dp[p2] * 2: p2 += 1
            if value == dp[p3] * 3: p3 += 1
            if value == dp[p5] * 5: p5 += 1
            i += 1
        return dp[n-1]