Algorithmic Getting Started note------------Day3

The main part is to review the basic contents of the previous, and the concept of function

Number of combinations

#include <stdio.h>int f (int n) {        int m=1;        for (int i=1;i<=n;i++)            m*=i;        return m;} int main (void) {        int n,m;        scanf ("%d%d", &n,&m);        printf ("%d\n", f (N)/(f (M) *f (n-m)));        return 0;}

Prime number of twins

 #include <stdio.h>int isprime (int n) {int i;        for (i=2;i*i<=n;i++) if (n%i==0) return 0; return 1;}        int main (void) {int m;        scanf ("%d", &m);                    for (int i=m-2;i>=3;i--) {if (IsPrime (i) &&isprime (i+2)) {                    printf ("%d%d\n", i,i+2);                Break }} return 0;}        #include <stdio.h> #include <math.h> #include <assert.h>int isprime (int x) {int i,m;        ASSERT (x>=0);        M=floor (sqrt (x) +0.5);        for (i=2;i<=m;i++) if (x%i==0) return 0; return 1;}        int main (void) {int i,m;        scanf ("%d", &m);                        for (i=m-2;i>=3;i--) {if (IsPrime (i) &&isprime (i+2)) {                        printf ("%d%d\n", i,i+2);                    Break }} return 0;} 

Exchange function pointers are used, multiple values are returned

int swap (int *a,int *b) {    t=*a;*a=*b;*b=t;}

Note the use of GDB

GCC test.c-g

GDB a.out (gdb a.exe)

Definition of recursion

　　

Algorithmic Getting Started note------------Day3