1.素数问题
代码：
#include "stdio.h"
void main() {
int a[100];
int k = 0;
int i = 0;
while(i < 100) {
int j = 2;
while (j < i) {
if(i%j == 0) {
break;
}
j++;
}
if(j == i) {
a[k++] = i;//等于于a[k] = i; k++;
//printf("%d,", i);
}
i++;
}
for(int i = 0; i < k; i++) {
printf("%d,", a[i]);
}
}
2.排序问题
代码：
#include "stdio.h"
void main() {
int a[10] = {21,1,32,43,6,321,5,23,16,10};
int temp = 0;
printf("The num sort:");
for(int i = 0; i < 10; i++) {
for(int j = i; j < 10; j++) {
if(a[i] > a[j]) {
temp = a[j];
a[j] = a[i];
a[i] = temp;
}
}
printf("%d,", a[i]);
}
}
输出结果：
3. 求矩阵对角线之和
代码：
#include "stdio.h"
void main() {
int a[3][3] = { {1,2,3},
{4,5,6},
{7,8,9}};
int sum = 0;
for(int i = 0; i < 3; i++) {
for(int j = 0; j < 3; j++){
if(i == j) {
sum = sum + a[i][j];
printf("a[%d][%d] = %d\n", i, j, a[i][j]);
}
}
}
printf("The sum is:%d", sum);
}
输出结果：
4.有序数组插入数据
代码：
#include "stdio.h"
void main() {
int a[20] = {1,3,5,7,9,14,20,34,50,100};
int temp = 0;
int num = 39;
printf("The numbers befor insert a number:");
for(int j = 0; j < 10; j++) {
printf(",%d", a[j]);
}
int i = 0;
while(a[i]) {
if(num <= a[i]) {
break;
}
i++;
}
for(int j = 10; j > i; j--) {
a[j] = a[j-1];
}
a[i] = num;
printf("\nThe numbers after insert a number:");
for(int j = 0; j < 11; j++) {
printf(",%d", a[j]);
}
}输出结果：
6.输出杨辉三角形
代码：
#include "stdio.h"
void main() {
int n = 10;
int a[10][10];
for(int i = 0; i < 10; i++) {
for(int j = 0; j < 10; j++) {
if(j == 0 && i != j) {
a[i][j] = 1;
printf("%d ", a[i][j]);
} else if(i == j) {
a[i][j] = 1;
printf("%d\n", a[i][j]);
} else if(i > j && j > 0) {
a[i][j] = a[i-1][j] + a[i-1][j-1];
printf("%d ", a[i][j]);
}
}
}
}
输出结果：
8. 鞍点问题
代码：
#include "stdio.h"
void main() {
int n = 10;
int a[3][3] = { {1,2,3},
{4,5,6},
{7,8,9}};
int max = 0;
int isMin = 1;
int col = 0;
for(int i = 0; i < 3; i++) {
for(int j = 0; j < 3; j++) {
if(max < a[i][j]) {
max = a[i][j];
col = j;
}
}
for(int k = 0; k < 3; k++) {
if(k!= i && max > a[k][col]) {
isMin = 0;
break;}
}
if(isMin) printf("a[%d][%d] = %d\n", i, col, a[i][col]);
}
}
输出结果：
9. 二分查找
代码：
#include "stdio.h"
void main() {
int a[15] = {1,3,5,7,9,14,20,34,50,100,123,134,234,5643,34893};
int n = 15;
int num = 0;
int center = n/2;
int flag = 0;
printf("Please input a number to find:");
scanf("%d", &num);
if(num > a[14] || num < a[0]) {
printf("No number!");
return;
}
for(int j = 0; j <= n; j++) {
if (num == a[center]) {
printf("the num has been found:a[%d] = %d", j, a[center]);
flag = 1;
break;
} else if(num < a[center]) {
n = center;
center = (j + center)/2;
} else {
j = center;
center = (center + n)/2;
}
//printf(",%d", center);
}
if(!flag) printf("No number!");
}
输出结果：
10. 解析字符数组中的字符类型
代码：
#include "stdio.h"
void main() {
char str[3][80] = { "feo390000000afdfff fffffadhfhqweh9hidhafhdaf8haifhadhf9h9hfhhfahf9w8hhdj[fs]",
"feo390000000afdffffffffffffadhfhqweh9hidhafhdaf8haifhadhf9h9hfhhfahf9w8hhdj[fs]",
"feo390000000afdfffffAAAAAffadhfhqweh9hidhafhdaf8haifhadhf9h9hfhhfahf9w8hhdj[fs]"};
int a = 0;//count number
int k = 0;//count big charactor
int l = 0;//count small charactor
int m = 0;//count space
int n = 0;//other chars
for(int i = 0; i < 3; i++) {
for(int j = 0; j < 80; j++){
if(str[i][j] >= '0' && str[i][j] <= '9') {
a++;
} else if(str[i][j] >= 'a' && str[i][j] <= 'z') {
l++;
} else if(str[i][j] >= 'A' && str[i][j] <= 'Z'){
k++;
}else if(str[i][j] == ' ') {
m++;
} else {
n++;
}
}
}
printf("The count of number is :%d\n", a);
printf("The count of big char is :%d\n", k);
printf("The length of small char is :%d\n", l);
printf("The count of space is :%d\n", m);
printf("The count of other chars is :%d", n);
}
输出结果：
11. 输出平行四边形图案
代码：
#include "stdio.h"
void main() {
int m = 0;
int n = 9;
for(int i = 0; i < 5; i++) {
for(int j = 0; j < 9; j++) {
if(j >= m && j <= m + 4) {
printf("*");
} else {
printf(" ");
}
}
m++;
printf("\n");
}
}
输出结果：
12. 字符编码解码
代码：
#include "stdio.h"
void main() {
char a[] = "Welcome to China!";
int i = 0;
while (a[i])
{
if(a[i] >= 'A' && a[i] <= 'Z') {
//int A = 'A';//97 'Z'=123
int j = a[i] - 'A';
a[i] = 'A' + 25 - j;
} else if(a[i] >= 'a' && a[i] <= 'z') {
int x = a[i] - 'a';
a[i] = 'a' + 25 - x;
}
i++;
}
printf("the encoded string is %s\n", a);
i = 0;
while (a[i])
{
if(a[i] >= 'A' && a[i] <= 'Z') {
//int A = 'A';//97 'Z'=123
int j = a[i] - 'A';
a[i] = 'A' + 25 - j;
} else if(a[i] >= 'a' && a[i] <= 'z') {
int x = a[i] - 'a';
a[i] = 'a' + 25 - x;
}
i++;
}
printf("the decoded string is %s\n", a);
}
输出结果：
13. 字符串连接实现
代码：
#include "stdio.h"
void main() {
char a[] = "Welcome to China!";
char b[] = "My dear friend.";
char c[200];
int i = 0;
while (a[i])
{
c[i] = a[i];
i++;
}
int length = i;
i = 0;
while (b[i])
{
c[i + length] = b[i];
i++;
}
c[i + length] = '\0';//字符串结尾加0，以免多余的字符显示
printf("the connected string is %s\n", c);
}
输出结果：
14. 字符串比较实现
#include "stdio.h"
int strCompare(char *a, char *b);
int strCompare(char *a, char *b){
int i = 0;
while (a[i] && b[i])
{
if(a[i] != b[i]) {
return a[i] - b[i];
}
i++;
}
if(a[i] == b[i]) {
return 0;
} else if(a[i] == 0) {
return -26;
} else if(b[i] == 0) {
return 26;
}
}
void main() {
char a[100];
char b[100];
printf("Please input string a:");
gets(a);
printf("Please input string b:");
gets(b);
int result = strCompare(a, b);
if(result == 0) {
printf("the compared strings equal\n");
} else if(result > 0) {
printf("the compared strings a long\n");
} else {
printf("the compared strings b long");
}
}
输出结果：
15. 字符串复制实现
代码：
#include "stdio.h"
void main() {
char a[] = "Welcome to China!";
char c[200];
int i = 0;
while (a[i])
{
c[i] = a[i];
i++;
}
c[i] = a[i];
printf("the copy string is %s\n", c);
}
输出结果：
