LeetCode Solutions
class Solution {
public:
bool verifyPreorder(vector<int>& preorder) {
int i = 0;
dfs(preorder, i, INT_MIN, INT_MAX);
return i == preorder.size();
}
private:
void dfs(const vector<int>& preorder, int& i, int min, int max) {
if (i == preorder.size())
return;
if (preorder[i] < min || preorder[i] > max)
return;
const int val = preorder[i++];
dfs(preorder, i, min, val);
dfs(preorder, i, val, max);
}
};
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class Solution {
public boolean verifyPreorder(int[] preorder) {
dfs(preorder, Integer.MIN_VALUE, Integer.MAX_VALUE);
return i == preorder.length;
}
private int i = 0;
private void dfs(int[] preorder, int min, int max) {
if (i == preorder.length)
return;
if (preorder[i] < min || preorder[i] > max)
return;
final int val = preorder[i++];
dfs(preorder, min, val);
dfs(preorder, val, max);
}
}
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class Solution:
def verifyPreorder(self, preorder: List[int]) -> bool:
i = 0
def dfs(min: int, max: int) -> None:
nonlocal i
if i == len(preorder):
return
if preorder[i] < min or preorder[i] > max:
return
val = preorder[i]
i += 1
dfs(min, val)
dfs(val, max)
dfs(-math.inf, math.inf)
return i == len(preorder)
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