C语言程序设计课件（英文）C program language 之5 Function and Program Structure.ppt

Contents Example Using Recursion: Fibonacci Series Fibonacci series: 0, 1, 1, 2, 3, 5, 8... Each number is the sum of the previous two Can be solved recursively: fib( n ) = fib( n - 1 ) + fib( n – 2 ) Code for the fibonacci function long fibonacci( long n ) { if (n == 0 || n == 1) /* base case */ return n; else return fibonacci( n - 1) + fibonacci( n – 2 ); } Recursion Set of recursive calls for fibonacci Recursion When input the number 12345 ，please output 54321 Steps: (1) How to output one digit : printf(“%d”,….); (2) How to output the code on the lowest-digits of N digits int unmeber. (3) The number is divided by 10， (4) The original problem is narrowed to the same question,but N – 1 digits (5) Test the codition , if true, execute step （6）, otherwise get back to step（2）。 (6) End of recursion calling 。 The digits are generated in the wrong order: low-order digits are available before high-order digits, but they have to be printed the other way around. Recursion 1 2 3 4 5 5 1 2 3 4 5 4 1 2 3 5 4 3 1 2 5 4 3 2 1 5 4 3 2 1 Note: 1. How to predigest the problem . 2.How to control the end of recursion 。 Recursion Output the value in reverse order （int N） { if（N =10）then { output the lowest digit； N is divided 10 N---N-1； call function itself（ N---N-1 ）; }else output N; } main( ) { int x; printf(“\nEnter N=”); scanf(“%d”,x); int_turn(x); } int_turn(n) int n; { if(n=10) { printf(“%d ”,n%10); int_turn(n/10); } else printf(“%d”,n); } Recursion void move(char getone, char putone) { printf(%c---%c\n,getone,putone); } void hanoi(int n,char one,char two,char three) { if(n==1) move(one,three); else { hanoi(n-1,one,three,two); move(one,three); hanoi(n-1,two,one,three); } } main() { int m; printf(Input the number of disks:); scanf(%d,m); printf(The steps to moving %3d disks:\n,m); hanoi(m,A,B,C); } Hanoi