笔试题集锦(编程题)
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题目描述
输入一个整数数组,判断该数组是不是某二叉搜索树的后序遍历的结果。如果是则输出Yes,否则输出No。假设输入的数组的任意两个数字都互不相同。
public boolean VerifySquenceOfBST( int [] sequence) { if (sequence.length== 0 ) return false ; if (sequence.length== 1 ) return true ; return ju(sequence, 0 , sequence.length- 1 ); } public boolean ju( int [] a, int star, int root){ if (star>=root) return true ; int i = root; //从后面开始找 while (i>star&&a[i- 1 ]>a[root]) i--; //找到比根小的坐标 //从前面开始找 star到i-1应该比根小 for ( int j = star;j<i- 1 ;j++) if (a[j]>a[root]) return false ;; return ju(a,star,i- 1 )&&ju(a, i, root- 1 ); } } class Solution { public: bool VerifySquenceOfBST(vector<int> sequence) { int size = sequence.size(); if(0==size) { return false; } return isLastOrder(sequence, 0, size-1); } private: bool isLastOrder(vector<int>& sequece, int b, int e) { if(b==e) { return true; } int mid = b; while(sequece[mid++]<sequece[e] && mid<e); int tmp = mid; while (sequece[tmp++]>sequece[e] && tmp<e); if(tmp<e) { return false; } if(mid==b || mid==e) { return isLastOrder(sequece, b, e-1); } else { return (isLastOrder(sequece, b, mid-1) && isLastOrder(sequece, mid, e-1)); } } };*/ //非递归 class Solution { public: bool VerifySquenceOfBST(vector<int> sequence) { int size = sequence.size(); if(0==size)return false; int i = 0; while(--size) { while(sequence[i++]<sequence[size]); while(sequence[i++]>sequence[size]); if(i<size)return false; i=0; } return true; } }; |
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