iOS 算法~面試題

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1、對以下一組數(shù)據(jù)進行降序排序(冒泡排序)。“24,17,85,13,9,54,76,45,5,63”

int main(int argc, char *argv[]) {

int array[10] = {24, 17, 85, 13, 9, 54, 76, 45, 5, 63};

int num = sizeof(array)/sizeof(int);

for(int i = 0; i < num-1; i++) {

for(int j = 0; j < num - 1 - i; j++) {

if(array[j] < array[j+1]) {

int tmp = array[j];

array[j] = array[j+1];

array[j+1] = tmp;

}}}

for(int i = 0; i < num; i++) {

printf("%d", array[i]);

if(i == num-1) {

printf("\n");

}else {

printf(" ");

}}}

2、對以下一組數(shù)據(jù)進行升序排序(選擇排序)。“86, 37, 56, 29, 92, 73, 15, 63, 30, 8”

void sort(int a[],int n)

{

int i, j, index;

for(i = 0; i < n - 1; i++) {

index = i;

for(j = i + 1; j < n; j++) {

if(a[index] > a[j]) {

index = j;

}}

if(index != i) {

int temp = a[i];

a[i] = a[index];

a[index] = temp;

}}}

int main(int argc, const char * argv[]) {

int numArr[10] = {86, 37, 56, 29, 92, 73, 15, 63, 30, 8};

sort(numArr, 10);

for (int i = 0; i < 10; i++) {

printf("%d, ", numArr[i]);

}

printf("\n");

return 0;

}

3、如何實現(xiàn)鏈表翻轉(zhuǎn)(鏈表逆序)?

思路:每次把第二個元素提到最前面來。

#include

#include

typedef struct NODE {

struct NODE *next;

int num;

}node;

node *createLinkList(int length) {

if (length <= 0) {

return NULL;

}

node *head,*p,*q;

int number = 1;

head = (node *)malloc(sizeof(node));

head->num = 1;

head->next = head;

p = q = head;

while (++number <= length) {

p = (node *)malloc(sizeof(node));

p->num = number;

p->next = NULL;

q->next = p;

q = p;

}

return head;

}

void printLinkList(node *head) {

if (head == NULL) {

return;

}

node *p = head;

while (p) {

printf("%d ", p->num);

p = p -> next;

}

printf("\n");

}

node *reverseFunc1(node *head) {

if (head == NULL) {

return head;

}

node *p,*q;

p = head;

q = NULL;

while (p) {

node *pNext = p -> next;

p -> next = q;

q = p;

p = pNext;

}

return q;

}

int main(int argc, const char * argv[]) {

node *head = createLinkList(7);

if (head) {

printLinkList(head);

node *reHead = reverseFunc1(head);

printLinkList(reHead);

free(reHead);

}

free(head);

return 0;

}

4、給定一個字符串,輸出本字符串中只出現(xiàn)一次并且最靠前的那個字符的位置?如“abaccddeeef”,字符是b,輸出應(yīng)該是2。

char *strOutPut(char *);

int compareDifferentChar(char, char *);

int main(int argc, const char * argv[]) {

char *inputStr = "abaccddeeef";

char *outputStr = strOutPut(inputStr);

printf("%c \n", *outputStr);

return 0;

}

char *strOutPut(char *s) {

char str[100];

char *p = s;

int index = 0;

while (*s != '\0') {

if (compareDifferentChar(*s, p) == 1) {

str[index] = *s;

index++;

}

s++;

}

return &str;

}

int compareDifferentChar(char c, char *s) {

int i = 0;

while (*s != '\0' && i<= 1) {

if (*s == c) {

i++;

}

s++;

}

if (i == 1) {

return 1;

} else {

return 0;

}

5、打印2-100之間的素數(shù)。

[cpp] view plain copy

int main(int argc, const char * argv[]) {

for (int i = 2; i < 100; i++) {

int r = isPrime(i);

if (r == 1) {

printf("%ld ", i);

}

}

return 0;

}

int isPrime(int n){

int i, s;

for(i = 2; i <= sqrt(n); i++)

if(n % i == 0)? return 0;

return 1;

}

6、求兩個整數(shù)的最大公約數(shù)。

[cpp] view plain copy

int gcd(int a, int b) {

int temp = 0;

if (a < b) {

temp = a;

a = b;

b = temp;

}

while (b != 0) {

temp = a % b;

a = b;

b = temp;

}

return a;

}

7、歸并排序

void merge(int sourceArr[], int tempArr[], int startIndex, int midIndex, int endIndex) {

int i = startIndex;

int j = midIndex + 1;

int k = startIndex;

while (i != midIndex + 1 && j != endIndex + 1) {

if (sourceArr[i] >= sourceArr[j]) {

tempArr[k++] = sourceArr[j++];

} else {

tempArr[k++] = sourceArr[i++];

}

}

while (i != midIndex + 1) {

tempArr[k++] = sourceArr[i++];

}

while (j != endIndex + 1) {

tempArr[k++] = sourceArr[j++];

}

for (i = startIndex; i <= endIndex; i++) {

sourceArr[i] = tempArr[i];

}

}

void sort(int souceArr[], int tempArr[], int startIndex, int endIndex) {

int midIndex;

if (startIndex < endIndex) {

midIndex = (startIndex + endIndex) / 2;

sort(souceArr, tempArr, startIndex, midIndex);

sort(souceArr, tempArr, midIndex + 1, endIndex);

merge(souceArr, tempArr, startIndex, midIndex, endIndex);

}

}

int main(int argc, const char * argv[]) {

int numArr[10] = {86, 37, 56, 29, 92, 73, 15, 63, 30, 8};

int tempArr[10];

sort(numArr, tempArr, 0, 9);

for (int i = 0; i < 10; i++) {

printf("%d, ", numArr[i]);

}

printf("\n");

return 0;

}

8、二叉樹的先序遍歷為FBACDEGH,中序遍歷為:ABDCEFGH,請寫出這個二叉樹的后序遍歷結(jié)果。

ADECBHGF

先序+中序遍歷還原二叉樹:先序遍歷是:ABDEGCFH中序遍歷是:DBGEACHF

首先從先序得到第一個為A,就是二叉樹的根,回到中序,可以將其分為三部分:

左子樹的中序序列DBGE,根A,右子樹的中序序列CHF

接著將左子樹的序列回到先序可以得到B為根,這樣回到左子樹的中序再次將左子樹分割為三部分:

左子樹的左子樹D,左子樹的根B,左子樹的右子樹GE

同樣地,可以得到右子樹的根為C

類似地將右子樹分割為根C,右子樹的右子樹HF,注意其左子樹為空

如果只有一個就是葉子不用再進行了,剛才的GE和HF再次這樣運作,就可以將二叉樹還原了。

9、打印2-100之間的素數(shù)。

int main(int argc, const char * argv[]) {

for (int i = 2; i < 100; i++) {

int r = isPrime(i);

if (r == 1) {

printf("%ld ", i);

}

}

return 0;

}

int isPrime(int n)

{

int i, s;

for(i = 2; i <= sqrt(n); i++)

if(n % i == 0)? return 0;

return 1;

}

10、實現(xiàn)一個字符串“how are you”的逆序輸出(編程語言不限)。如給定字符串為“hello world”,輸出結(jié)果應(yīng)當為“world hello”。

[cpp] view plain copy

int spliterFunc(char *p) {

char c[100][100];

int i = 0;

int j = 0;

while (*p != '\0') {

if (*p == ' ') {

i++;

j = 0;

} else {

c[i][j] = *p;

j++;

}

p++;

}

for (int k = i; k >= 0; k--) {

printf("%s", c[k]);

if (k > 0) {

printf(" ");

} else {

printf("\n");

}

}? ? return 0;

}

11、給定一個字符串,輸出本字符串中只出現(xiàn)一次并且最靠前的那個字符的位置?如“abaccddeeef”,字符是b,輸出應(yīng)該是2。

[cpp] view plain copy

char *strOutPut(char *);

int compareDifferentChar(char, char *);

int main(int argc, const char * argv[]) {

char *inputStr = "abaccddeeef";

char *outputStr = strOutPut(inputStr);

printf("%c \n", *outputStr);

return 0;

}

char *strOutPut(char *s) {

char str[100];

char *p = s;

int index = 0;

while (*s != '\0') {

if (compareDifferentChar(*s, p) == 1) {

str[index] = *s;

index++;

}

s++;

}

return &str;

}

int compareDifferentChar(char c, char *s) {

int i = 0;

while (*s != '\0' && i<= 1) {

if (*s == c) {

i++;

}

s++;

}

if (i == 1) {

return 1;

} else {

return 0;

}

}

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