C_输入一个整数N，输出从0~N（算法思考）

1.for循环实现

 #include <stdio.h>
 #include <time.h>

 clock_t start, stop;
 double duration;

 void printfN();

 int main(){
     int N;
     printf("Pleade enter a number: ");
     scanf("%d", &N);
     start = clock();
     printfN(N);
     stop = clock();
     duration = ((double)(stop - start))/CLK_TCK;
     printf("duration = %f\n",duration);
     return ;
 }

 void printfN(int N){
     int i;
     for(i=; i<=N; i++){
         printf("%d\n",i);
     }
 }

2.递归实现（有问题，思考——算法的执行效率与输入规模的关系）

 #include <stdio.h>
 #include <time.h>

 void printfN();

 clock_t start, stop;
 double duration;

 int main(){
     int N;
     printf("Please enter a number:");
     scanf("%d", &N);
     start = clock();
     printfN(N);/*12000程序无法运行*/
     stop = clock();
     duration = ((double)(stop - start))/CLK_TCK;
     printf("duration = %f\n",duration);
     return ;
 }

 void printfN(N){
     if(N){
         printfN(N-);
     }
     printf("%d\n",N);
 }