题目源自: Linux C编程一站式学习的习题

欢迎拍砖~

c版

#include <stdio.h>
#define N 5
#define M 5
#define IS_COMBINATION 1

int arr[N];

void printArr(void){
	int j = M,i ;
	if(IS_COMBINATION){
		for(i=0;i<M-1;i++){
			if(arr[i]>arr[i+1])return;
		}
	}
	for(i=0;i<j;i++){
		printf("%d ",arr[i]);
	}
	printf("\n");
}

void swap(int i , int j){
	int temp = arr[i];arr[i]=arr[j];arr[j]=temp;
}

void permutation(int k){
	int i = N-k;
	if(k==N-M){
		printArr();
		return;
	}
	for(;i<N;i++){
		swap(N-k,i);
		permutation(k-1);
		swap(N-k,i);
	}
}

int main(void){
	int i = 0 ;
	for(;i<N;i++ ){arr[i]=i+1;}
	permutation(N );
	return 0;
}

?

java版

	static int N = 5,M=3;
	static boolean IS_COMBINATION = false;
	
	static int[] arr = new int[N];
	
	static void print(){
		if(IS_COMBINATION){
	        for(int i=0;i<M-1; i++){
		            if(arr[i]>arr[i+1]){
		                return;
		            }
	            }
        }
		System.out.println(Arrays.toString(Arrays.copyOfRange(arr, 0, M)));
	}
	
	static void swap(int i , int j){
		arr[i]=arr[j]+0*(arr[j]=arr[i]);
	}
	
	static void permutation(int k){
		if(k==N-M){
			print();
			return;
		}
		for (int i = N-k; i < N; i++) {
			swap(i, N-k);
			permutation(k-1);
			swap(i, N-k);
		}
	} 
	
	public static void main(String[] args) {
		for (int i = 0; i < N; i++) {
			arr[i]=i+1;
		}
		permutation(N);
	}

?

javascript版

var N = 5,M = 1 , IS_COMBINATION = true ;
var arr  = [] ;
for(var i = 0 ; i<N  ;i++){
    arr[i]=i+1;
}

var print = function(){
    if(IS_COMBINATION){
        for(var i=0;i<M-1; i++){
            if(arr[i]>arr[i+1]){
                console.log(arr);
                return;
            }
        }
    }
    console.log(arr.slice(0,M));
}

var swap = function(i,j){
    arr[i]=arr[j]+0*(arr[j]=arr[i]);
}

var permutation = function(k){
    if(k==N-M){
        print();
        return;
    }
    for(var i = N-k ; i< N  ; i++){
        swap(N-k,i);
        permutation(k-1);
        swap(N-k,i);
    }
}

permutation(N);

?