（算法）完美洗牌

#include<iostream>
#include<stdlib.h>
#include<time.h>
using namespace std;

int rnd(int lower,int higher){
    return rand()%(higher-lower+1)+lower;
}

void shuffle_1(int *cards,int n){
    if(n==1)
        return;

    shuffle_1(cards,n-1);

    int k=rnd(0,n-1);

    int tmp=cards[k];
    cards[k]=cards[n-1];
    cards[n-1]=tmp;
}

void shuffle_2(int *cards,int n){
    for(int i=0;i<n;i++){
        int k=rnd(0,i);
        int tmp=cards[k];
        cards[k]=cards[i];
        cards[i]=tmp;
    }    
}

int main(){
    srand((unsigned)time(0));
    int cards[52];
    for(int i=0;i<52;i++)
        cards[i]=i+1;
    shuffle_1(cards,52);
    shuffle_2(cards,52);
    return 0;    
}