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剑指 Offer II 022. 链表中环的入口节点（无题解）
面试题 02.08. 环路检测（无题解）
题解
void visit(struct TreeNode *root,int *ans,int *ansnum){
if(root){
if(root->left) visit(root->left,ans,ansnum);
if(root->right) visit(root->right,ans,ansnum);
ans[(*ansnum)++] = root->val;
}
}//后序遍历 保存到栈
int* postorderTraversal(struct TreeNode* root, int* returnSize){
int *ans= malloc(sizeof(int)*101),ansnum = 0;
visit(root,ans,&ansnum);
*returnSize = ansnum;
return ans;
}
void inorder(struct TreeNode* root,int *a,int *b);
int* inorderTraversal(struct TreeNode* root, int* returnSize){
int *ans= malloc(sizeof(int)*100),anssize= 0;
*returnSize = 0;
inorder(root,ans,returnSize);
return ans;
}
void inorder(struct TreeNode* root,int *a,int *b){
if(root){
inorder(root->left,a,b);
a[(*b)++] = root->val;
inorder(root->right,a,b);
}
}//后续遍历 直接保存
int* nextGreaterElement(int* nums1, int nums1Size, int* nums2, int nums2Size, int* returnSize){
int *ans = malloc(sizeof(int)*100010);
for(int i = 0;i < nums1Size;i++){
ans[i] = nums1[i];
int j = 0;
while(j<nums2Size&&nums2[j]!=ans[i]) j++;
for(;j <nums2Size;j++)
if(ans[i] < nums2[j]) {
ans[i] = nums2[j];
break;
}
if(ans[i] == nums1[i]) ans[i] = -1;
}
*returnSize = nums1Size;
return ans;
}
int calPoints(char ** ops, int opsSize){
int stack[10000],top = 0,ans = 0;//top指向下一个元素
for(int i = 0;i <opsSize;i++){
if(ops[i][0] == '+') {//弹栈计算
int num2 = stack[top - 1],num1 = stack[top - 2];
stack[top++] = num1 + num2;
}
else if(ops[i][0] == 'C') top--; //出栈一个
else if(ops[i][0] == 'D'){
int num2 = stack[top - 1];
stack[top++] = num2 * 2;
}
else{//数字入栈
int j = 0,flag = 0,num = 0;
if(ops[i][0] == '-') flag = 1,j++;
for(;ops[i][j];j++){
num *= 10;
num += ops[i][j] - '0';
}
if(!flag) stack[top++] = num;
else stack[top++] = -num;
}
}
for(int i = 0;i < top;i++) ans+=stack[i];
return ans; //最后栈内只剩最终结果
}
void preord(struct Node* root,int *ans,int *num){
if(root){
ans[(*num)++] = root->val;
for(int i =0;i<root->numChildren;i++)
preord(root->children[i],ans,num);
}
}
int* preorder(struct Node* root, int* returnSize) {
int *ans = malloc(sizeof(int)*10000);
*returnSize = 0;
preord(root,ans,returnSize);
return ans;
}
void preord(struct Node* root,int *ans,int *num){
if(root){
for(int i =0;i<root->numChildren;i++)
preord(root->children[i],ans,num);
ans[(*num)++] = root->val;
}
}
int* postorder(struct Node* root, int* returnSize) {
int *ans = malloc(sizeof(int)*10000);
*returnSize = 0;
preord(root,ans,returnSize);
return ans;
}
bool backspaceCompare(char * s, char * t){
char ans1[210],ans2[210],top1 = 0,top2 = 0;
for(int i = 0;s[i];i++)
if(s[i] == '#'){
if(top1) top1--;
}
else ans1[top1++] = s[i];
for(int i = 0;t[i];i++){
if(t[i] == '#'){
if(top2) top2--;
}
else ans2[top2++] = t[i];
}
ans1[top1] = 0;
ans2[top2] = 0;
return !strcmp(ans1,ans2);
}
void zhongxu(struct TreeNode *root,struct TreeNode **ans,int *top){
if(root){
zhongxu(root->left,ans,top);
ans[(*top)++] = root; //插入队列中
zhongxu(root->right,ans,top);
}
}
struct TreeNode* increasingBST(struct TreeNode* root){
struct TreeNode* ans[101];
memset(ans,0,sizeof(ans));
int top =0;
zhongxu(root,ans,&top);
for(int i = 0;i < top;i++){
ans[i]->left = 0;
ans[i]->right = ans[i+1];
}
return ans[0];
}
int sremove(char *s){
int ans = 0;
char temp[100100];
int top = 0;
for(int i = 0;s[i];i++)
if(top&&s[i] == temp[top - 1]) top--,ans++;
else temp[top++] = s[i];
int size = 0;
for(int i = 0;i <top;i++)
s[size++] = temp[i];
s[size] = 0;
return ans;
}
char * removeDuplicates(char * s){
sremove(s);
return s;
}
int evalRPN(char ** tokens, int tokensSize){
for(int i = 0;i <tokensSize;i++){
if(top) printf("%d",stack[top-1]);
if(tokens[i][0] == '+') {//弹栈计算
int num2 = stack[--top],num1 = stack[--top];
stack[top++] = num1 + num2;
}
else if(tokens[i][0] == '-' && !tokens[i][1]){
int num2 = stack[--top],num1 = stack[--top];
stack[top++] = num1 - num2;
}
else if(tokens[i][0] == '*'){
int num2 = stack[--top],num1 = stack[--top];
stack[top++] = num1 * num2;
}
else if(tokens[i][0] == '/'){
int num2 = stack[--top],num1 = stack[--top];
stack[top++] = num1 / num2;
}
else{//数字入栈
int j = 0,flag = 0,num = 0;
if(tokens[i][0] == '-') flag = 1,j++;
for(;tokens[i][j];j++){
num *= 10;
num += tokens[i][j] - '0';
}
if(!flag) stack[top++] = num;
else stack[top++] = -num;
}
}
return stack[0]; //最后栈内只剩最终结果
}
char * decodeString(char * s){
char *stack =malloc(sizeof(char)*100000);
int top = 0;
for(int i = 0;s[i];i++){
if(s[i] ==']'){ //出栈
char temp[10000];
int tempnum = 0;
while(stack[--top]!='[') temp[tempnum++] = stack[top];
unsigned char k = stack[--top];//个数弹出来 这里有个坑，这玩意是有符号的。。。离谱！
while(k--)
for(int m = tempnum - 1;m>=0;m--)
stack[top++] = temp[m];
}
else if(s[i] >='0'&&s[i]<='9'){
int temp = 0;
while(s[i] >='0'&&s[i]<='9'){
temp *= 10;
temp+=s[i] - '0';
i++;
}
stack[top++] = temp;
i--;
}
else stack[top++] = s[i];//入栈
}
stack[top] = 0;
return stack;
}