文章目錄
11.二進制中1的個數
class Solution {
public:
int NumberOf1(int n) {
int ret = 0;
for(int i=0; i<sizeof(int)*8; i++) //不能使用 while(n != 0)
//負數用補碼錶示，而移位是算術移位，如果是負數移位後會在最高位補1，那麼就不能正確統計個數，而且程序會死循環
{
if(n & 1 == 1)
ret++;
n = n>>1;
}
return ret;
}
};
12.數值的整數次方
遞歸
class Solution {
public:
double Power(double base, int exponent) {
bool isNegative = (exponent < 0)?true:false;
exponent = abs(exponent);
if(exponent == 0)
return 1;
double ret = Power(base, exponent/2);
ret = (exponent%2 == 0)?ret*ret:ret*ret*base;
if(isNegative)
ret = 1/ret;
return ret;
}
};
13.調整數組順序使奇數位於偶數前面
開闢一個新數組，然後將調好序的數組賦值給原數組
class Solution {
public:
void reOrderArray(vector<int> &array) {
if(array.size() <= 1)
return ;
int num = 0;
for(int i=0; i<array.size(); i++)
if(array[i]%2 != 0)
num++;
vector<int> help(array.size(), -1);
int index_even = num;
int index_odd = 0;
for(int i=0; i<array.size(); i++)
{
if(array[i]%2 != 0)
help[index_odd++] = array[i];
else
help[index_even++] = array[i];
}
array.swap(help);
}
};
14.鏈表中倒數第k個結點
/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* FindKthToTail(ListNode* pListHead, unsigned int k) {
if(!pListHead)
return NULL;
ListNode *pre = pListHead;
ListNode *cur = pListHead;
while(pre && k>0)
{
k--;
pre = pre->next;
}
if(k != 0)
return NULL;
while(pre)
{
pre = pre->next;
cur = cur->next;
}
return cur;
}
};
15.反轉鏈表
/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* ReverseList(ListNode* pHead) {
if(!pHead)
return NULL;
ListNode *dummyHead = new ListNode(-1);
dummyHead->next = pHead;
ListNode *cur = pHead->next;
pHead->next = NULL;
while(cur)
{
ListNode *tmp = cur->next;
cur->next = dummyHead->next;
dummyHead->next = cur;
cur = tmp;
}
return dummyHead->next;
}
};
16.合併兩個排序的鏈表
/*
struct ListNode {
int val;
struct ListNode *next;
ListNode(int x) :
val(x), next(NULL) {
}
};*/
class Solution {
public:
ListNode* Merge(ListNode* pHead1, ListNode* pHead2)
{
if(!pHead1 && pHead2)
return pHead2;
if(pHead1 && !pHead2)
return pHead1;
ListNode *pHead3 = new ListNode(-1);
ListNode *l1 = pHead1;
ListNode *l2 = pHead2;
ListNode *l3 = pHead3;
while(l1 && l2)
{
if(l1->val <= l2->val)
{
ListNode *tmp = l1->next;
l3->next = l1;
l3 = l1;
l1 = tmp;
}
else{
ListNode *tmp = l2->next;
l3->next = l2;
l3 = l2;
l2 = tmp;
}
}
if(l1)
l3->next = l1;
else if(l2)
l3->next = l2;
return pHead3->next;
}
};
17.樹的子結構
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
bool HasSubtree(TreeNode* pRoot1, TreeNode* pRoot2)
{
if(!pRoot1 || !pRoot2)
return false;
return isSame(pRoot1, pRoot2) || HasSubtree(pRoot1->left, pRoot2) || HasSubtree(pRoot1->right, pRoot2);
}
bool isSame(TreeNode *pRoot1, TreeNode *pRoot2)
{
if(!pRoot1 && pRoot2)
return false;
if(!pRoot2)
return true;
return pRoot1->val==pRoot2->val && isSame(pRoot1->left, pRoot2->left) && isSame(pRoot1->right, pRoot2->right);
}
};
18.二叉樹的鏡像
/*
struct TreeNode {
int val;
struct TreeNode *left;
struct TreeNode *right;
TreeNode(int x) :
val(x), left(NULL), right(NULL) {
}
};*/
class Solution {
public:
void Mirror(TreeNode *pRoot) {
if(!pRoot)
return ;
Mirror(pRoot->left);
Mirror(pRoot->right);
TreeNode *tmp = pRoot->left;
pRoot->left = pRoot->right;
pRoot->right = tmp;
}
};
19. 順時針打印矩陣
class Solution {
public:
vector<int> printMatrix(vector<vector<int> > matrix) {
vector<int> ret;
int row = matrix.size();
int col = matrix[0].size();
int left = 0;
int top = 0;
int right = col-1;
int botton = row-1;
while(left<=right && top<=botton)
{
for(int i=left; i<=right; i++) //從左往右
ret.push_back(matrix[top][i]);
for(int i=top+1; i<=botton; i++) //從上往下
ret.push_back(matrix[i][right]);
if(top != botton) //避免只有一行
{
for(int i=right-1; i>=left; i--) //從右往左
ret.push_back(matrix[botton][i]);
}
if(left != right) //避免只有一列
{
for(int i=botton-1; i>top; i--) //從下往上
ret.push_back(matrix[i][left]);
}
left ++;
top ++;
right --;
botton --;
}
return ret;
}
};
20. 包含min函數的棧
class Solution {
public:
void push(int value) {
dataS.push(value);
if(minS.size() == 0)
minS.push(value);
else
minS.push(minS.top()<value?minS.top():value);
}
void pop() {
dataS.pop();
minS.pop();
}
int top() {
return dataS.top();
}
int min() {
return minS.top();
}
private:
stack<int> dataS; //數據棧
stack<int> minS; //最小值棧
};