#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(){

	char* c = (char*)malloc(sizeof(char)*20);
	char* d = (char*)malloc(sizeof(char)*10);
	c[20]='a';
	return 0;
}

#include<stdio.h>

int main(void){

	int a[5];
	int i,s;
	a[0]=a[1]=a[3]=a[4]=0;
	s = 0;
	for(i=0;i<5;++i){
		s+=a[i];
	}
	if(s == 377){
		printf("sum is = %d\n",s);
	}
	return 0;
}

#include<stdlib.h>
#include<stdio.h>

int main(){

	int len=4;
	int* pt = (int*)malloc(len*sizeof(int));
	
	int *p = pt;

	for(int i =0; i < len;++i){
		++p;
	}
	//over
	*p = 5;
	printf("the value of p equal: %d", *p);
	return 0;
}

#include<stdio.h>
#include<stdlib.h>
#include<string.h>
int main(){

	char x[50];
	for(int i = 0; i <50 ; ++i){
		x[i]=i+1;
	}

	strncpy(x+20,x,20);  //ok
	strncpy(x+20,x,21);  //overlap
	
	strncpy(x,x+20,20);  //ok
	strncpy(x,x+20,21);  //overlap

	x[39]='\0';
	strcpy(x,x+20);      //ok
	
	x[39]=39;
	x[40]='\0';
	strcpy(x,x+20);      //overlap

	return 0;
}

#include<stdio.h>
#include<stdlib.h>

int main(){

	char* p = (char* )malloc(10);
	char* pt=p;
	for(int i=0; i<10; ++i){
		p[i] = 'z';
	}

	delete p;

	pt[1]='x';
	free(pt);
	return 0;
}

#include<stdio.h>
#include<stdlib.h>

typedef struct _node{
	struct _node *l;
	struct _node *r;
	char v;

} node;

node* mk(node* l, node* r, char val){

	node* f = (node* )malloc(sizeof(node));
	f->l = l;
	f->r = r;
	f->v =val;
	return f;
}
void nodefr(node* n){
	if(n){
		nodefr(n->l);
		nodefr(n->r);
		free(n);
	}
}


int main(){

	node* t1,*t2,*t3;
	t1=mk(mk(mk(0,0,'3'),0,'2'),0,'1');

	t2=mk(0,mk(0,mk(0,0,'6'),'5'),'4');

	t3=mk(mk(t1,t2,'8'),0,'7');
	return 0;
}