【IT168 技术】C/C++ 经典算法实例 二分查找的代码。
int bfind(int* a,int len,int val)
{
int m = len/2;
int l = 0;
int r = len;
while(l!=m && r!= m)
{
if(a[m] > val)
{
r = m;
m = (m+l)/2;
}
else if(a[m] < val)
{
l = m;
m = (m+r)/2;
}
else
return m;
}
return -1; //没有找到
}
{
int m = len/2;
int l = 0;
int r = len;
while(l!=m && r!= m)
{
if(a[m] > val)
{
r = m;
m = (m+l)/2;
}
else if(a[m] < val)
{
l = m;
m = (m+r)/2;
}
else
return m;
}
return -1; //没有找到
}
写出在母串中查找子串出现次数的代码。
int count1(char* str,char* s)
{
char* s1;
char* s2;
int count = 0;
while(*str!='\0')
{
s1 = str;
s2 = s;
while(*s2 == *s1&&(*s2!='\0')&&(*s1!='0'))
{
s2++;
s1++;
}
if(*s2 == '\0')
count++;
str++;
}
return count;
}
{
char* s1;
char* s2;
int count = 0;
while(*str!='\0')
{
s1 = str;
s2 = s;
while(*s2 == *s1&&(*s2!='\0')&&(*s1!='0'))
{
s2++;
s1++;
}
if(*s2 == '\0')
count++;
str++;
}
return count;
}
查找第一个匹配子串位置，如果返回的是s1长度len1表示没有找到。
size_t find(char* s1,char* s2)
{
size_t i=0;
size_t len1 = strlen(s1)
size_t len2 = strlen(s2);
if(len1-len2<0) return len1;
for(;i {
size_t m = i;
for(size_t j=0;j {
if(s1[m]!=s2[j])
break;
m++;
}
if(j==len)
break;
}
return i
}
{
size_t i=0;
size_t len1 = strlen(s1)
size_t len2 = strlen(s2);
if(len1-len2<0) return len1;
for(;i {
size_t m = i;
for(size_t j=0;j {
if(s1[m]!=s2[j])
break;
m++;
}
if(j==len)
break;
}
return i
}
写出快速排序或者某种排序算法代码
快速排序：
int partition(int* a,int l,int r)
{
int i=l-1,j=r,v=a[r];
while(1)
{
while(a[++i] while(a[--j]>v) if(j<=i) break;
if(i>=j)
break;
swap(a[i],a[j]);
}
swap(a[i],a[r]);
return i;
}
void qsort(int* a,int l,int r)
{
if(l>=r) return;
int i = partition(a,l,r);
qsort(a,l,i-1);
qsort(a,i+1,r);
}
{
int i=l-1,j=r,v=a[r];
while(1)
{
while(a[++i] while(a[--j]>v) if(j<=i) break;
if(i>=j)
break;
swap(a[i],a[j]);
}
swap(a[i],a[r]);
return i;
}
void qsort(int* a,int l,int r)
{
if(l>=r) return;
int i = partition(a,l,r);
qsort(a,l,i-1);
qsort(a,i+1,r);
}
冒泡排序：
void buble(int *a,int n)
{
for(int i=0;i {
for(int j=1;j {
if(a[j] {
int temp=a[j];
a[j] = a[j-1];
a[j-1] = temp;
}
}
}
}
{
for(int i=0;i {
for(int j=1;j {
if(a[j] {
int temp=a[j];
a[j] = a[j-1];
a[j-1] = temp;
}
}
}
}
插入排序：
void insertsort(int* a,int n)
{
int key;
for(int j=1;j {
key = a[j];
for(int i=j-1;i>=0&&a[i]>key;i--)
{
a[i+1] = a[i];
}
a[i+1] = key;
}
}
{
int key;
for(int j=1;j {
key = a[j];
for(int i=j-1;i>=0&&a[i]>key;i--)
{
a[i+1] = a[i];
}
a[i+1] = key;
}
}
出现次数相当频繁
实现strcmp函数：
int strcmp11(char* l,char* r)
{
assert(l!=0&&r!=0);
while(*l == *r &&*l != '\0') l++,r++;
if(*l > *r)
return 1;
else if(*l == *r)
return 0;
return -1;
}
{
assert(l!=0&&r!=0);
while(*l == *r &&*l != '\0') l++,r++;
if(*l > *r)
return 1;
else if(*l == *r)
return 0;
return -1;
}
实现字符串翻转：
void reserve(char* str)
{
assert(str != NULL);
char * p1 = str;
char * p2 = str-1;
while(*++p2); //一般要求不能使用strlen
p2 -= 1;
while(p1 {
char c = *p1;
*p1++ = *p2;
*p2-- = c;
}
}
{
assert(str != NULL);
char * p1 = str;
char * p2 = str-1;
while(*++p2); //一般要求不能使用strlen
p2 -= 1;
while(p1 {
char c = *p1;
*p1++ = *p2;
*p2-- = c;
}
}
将一个单链表逆序：
struct list_node
{
list_node(int a,list_node* b):data(a),next(b) //这个为了测试方便
{}
int data;
list_node* next;
};
void reserve(list_node* phead)
{
list_node* p = phead->next;
if(p == NULL || p->next == NULL) return; //只有头节点或一个节点
list_node* p1=p->next;
p->next=NULL;
while(p1!=NULL)
{
p = p1->next;
p1->next = phead->next;
phead->next = p1;
p1 = p;
}
}
{
list_node(int a,list_node* b):data(a),next(b) //这个为了测试方便
{}
int data;
list_node* next;
};
void reserve(list_node* phead)
{
list_node* p = phead->next;
if(p == NULL || p->next == NULL) return; //只有头节点或一个节点
list_node* p1=p->next;
p->next=NULL;
while(p1!=NULL)
{
p = p1->next;
p1->next = phead->next;
phead->next = p1;
p1 = p;
}
}
