字符串全排列

分为递归法、循环法

#include <iostream>

#include <string.h>
using namespace std;

void swap(char * a, char * b) {
    char temp = * a;
    *a = *b;
    *b = temp;
}

void swapArea(char * a, char *b) {
    while( a < b)
        swap(a++,b--);

}


bool CanSwap(char * str, int start, int end) {
    for(int i = start; i <end; ++i) {
        if((*(str+i)) == *(str+end))
            return false;
    }
    return true;
}

void AllRange(char *str, int start, int end) {

    if( start == end) {
        cout <<str<<"\t";
    } else {

        for( int i = start; i <= end; ++i) {
            if(CanSwap(str,start,i)) {
                swap(str+start, str+i);
                AllRange(str, start+1, end);
                swap(str+start , str + i);
            }

        }
    }
}


bool hasNextPermutation(char *str) {
    char * pEnd = str +strlen(str);
    if(str == pEnd)
        return false;
    char *p, *q, *m;
    pEnd --;
    p = pEnd;
    while( p != str) {
        q= p;
        p--;
        if( *p < *q) {
            m= pEnd;
            while( *m <= *p)
                m--;

            swap(m,p);
            swapArea(m,pEnd);
            return true;
        }
    }
    swapArea(q,pEnd);
    return false;
}

void Permutation(char str[])
{
    if(str != NULL)
    {
        cout<<str<<endl;
        while(hasNextPermutation(str))
        {
            cout<<str<<endl;
        }
    }
}
int main() {
    cout << "Hello world!" << endl;
    char str[] = {"1224"};
    AllRange(str,0,strlen(str)-1);
    cout<<endl<<"____________________"<<endl;
    char test[]={"223"};
    Permutation(test);
    return 0;
}