//根据遍历序列确定二叉树
typedef struct BTNode
{
int data;
struct BTNode* lChild;
struct BTNode* rChild;
}BTNode;
//已知先序和中序遍历序列确定二叉树
BTNode *CreateBT(char pre[], char in[], int L1, int R1, int L2, int R2)
'''pre[],in[]存入确定遍历序列，
L1, R1为数组pre[]的操作范围,
L2, R2为数组in[]的操作范围'''
{
if (L1 > R1)
return NULL;
BTNode *s = (BTNode *)malloc(sizeof(BTNode));
s->lChild = s->rChild = NULL;
s->data = pre[L1];
int i;
for(i = L2; i <= R2; ++i)
{
if(in[i] == pre[L1])
break;//找到中序序列的双亲节点位置
}
s->lChild = CreateBT(pre, in, L1+1, L1+i-L2, L2, i-1);
s->rChild = CreateBT(pre, in, L1+i-L2+1, R1, i+1, R2);
}
//已知后序和中序遍历序列
BTNode *CreateBT2(char post[], char in[], int L1, int R1, int L2, int R2)
{
if (L1 > R1)
return NULL;
BTNode *s = (BTNode *)malloc(sizeof(BTNode));
s->lChild = s->rChild = NULL;
s->data = post[R1];
int i;
for(i = L2; i <= R2; ++i)
{
if(in[i] == post[R1])
break;//找到中序序列的双亲节点位置
}
s->lChild = CreateBT2(post, in, L1, L1+i-L2-1, L2, i-1);
s->rChild = CreateBT2(post, in, L1+i-L2, R1-1, i+1, R2);
}
//已知层次和中序遍历序列
int search(char arr[], char key, int L, int R)
{
int idx;
for(idx = L; idx <= R; ++idx)
{
if(arr[idx] = key)
return idx;
}
return -1
}
'''层次遍历序列中获取子序列'''
void getSubLevel(char subLevel[], char level[], char in[], int n, int L, int R)
{
int k =0;
for(int i = 0; i < n; ++i)
{
if (search(in, level[i], L, R) != -1)
subLevel[k++] = level[i];
}
}
BTNode *CreateBT3(char level[], char in[], int n, int L, int R)
{
if (L > R)
return NULL;
BTNode *s = (BTNode *)malloc(sizeof(BTNode));
s->lChild = s->rChild = NULL;
s->data = level[0];
//找到中序序列的双亲节点位置
int i = search(in, level[0], L, R);
//将中序序列分成左子序列、右子序列
int LN = i-N; char LLevel[LN];
int NR = R-i; char RLevel[NR];
getSubLevel(LLevel, level, in, n, L, i-1);
getSubLevel(RLevel, level, in, n, i+1, R);
s->lChild = CreateBT3(LLevel, in, LN, L, i-1);
s->rChild = CreateBT3(RLevel, in, NR, i+1, R);
return s;
}
//只知道先序和后序不能确定二叉树
