C language must memorize entry code-C#.Net Tutorial-php.cn

C language must memorize entry code

#1. Output the 9*9 formula. There are 9 rows and 9 columns in total, i controls the rows and j controls the columns.

#include "stdio.h" main() {int i,j,result; for (i=1;i<10;i++) { for(j=1;j<10;j++) { result=i*j; printf("%d*%d=%-3d",i,j,result);/*-3d表示左对齐，占3位*/ } printf("\n");/*每一行后换行*/ } }

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2. Determine how many prime numbers there are between 101-200, and output all prime numbers and the number of prime numbers.

Program analysis: How to determine prime numbers: Use a number to divide 2 to sqrt (this number) respectively. If it can be divided evenly, it means that the number is not a prime number, otherwise it is a prime number.

#include "math.h" main() { int m,i,k,h=0,leap=1; printf("\n"); for(m=101;m<=200;m++) { k=sqrt(m+1); for(i=2;i<=k;i++) if(m%i==0) {leap=0;break;} if(leap) /*内循环结束后，leap依然为1，则m是素数*/ {printf("%-4d",m);h++; if(h%10==0) printf("\n"); } leap=1; } printf("\nThe total is %d",h); }

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3. The function of the following program is to rotate a 4×4 array 90 degrees counterclockwise and then output it. The data of the original array is required to be randomly input, and the new array is arranged in 4 rows and 4 columns. Output

main() { int a[4][4],b[4][4],i,j; /*a存放原始数组数据，b存放旋转后数组数据*/ printf("input 16 numbers: "); /*输入一组数据存放到数组a中，然后旋转存放到b数组中*/ for(i=0;i<4;i++) for(j=0;j<4;j++) { scanf("%d",&a[i][j]); b[3-j][i]=a[i][j]; } printf("array b:\n"); for(i=0;i<4;i++) { for(j=0;j<4;j++) printf("%6d",b[i][j]); printf("\n"); } }

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4. Programming to print right-angled Yang Hui triangle

main() {int i,j,a[6][6]; for(i=0;i<=5;i++) {a[i][i]=1;a[i][0]=1;} for(i=2;i<=5;i++) for(j=1;j<=i-1;j++) a[i][j]=a[i-1][j]+a[i-1][j-1]; for(i=0;i<=5;i++) {for(j=0;j<=i;j++) printf("%4d",a[i][j]); printf("\n");} }

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