LC96_numTrees

题目

https://leetcode-cn.com/problems/unique-binary-search-trees/

解法

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public int numTrees(int n) {
if (n < 0) {
return -1;
}
if (n <= 1) {
return 1;
}

int[] dp = new int[n+1]; //
dp[0] = 1;
dp[1] = 1;
for (int i = 2; i < n+1; i++) {
for (int j = 1; j <= i; j++) {
dp[i] += dp[j-1] * dp[i-j];
}
}
return dp[n];
}
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