全排列/递归/八皇后问题

分别交换第1个元素与第2、3、4、5..len-1个元素

void permutation(char *str,int begin,int len){
	
	if(len==1){
		printf("%s\n",str);
		count++;
		return;	
	}
	char  tmp = str[begin];
	for(int i=0;i<len;i++){
		char  tmp2=str[begin+i];
		str[begin] = tmp2;
		str[begin+i] = tmp;
		permutation(str,begin+1,len-1);
		str[begin] = tmp;
		str[begin+i]=tmp2;
	}
	
}

        char str[6];
	strcpy(str,"12345");
	permutation(str,0,5);

求所有组合：http://zhedahht.blog.163.com/blog/static/2541117420114172812217/

void Combination(char* string, int number, vector<char>& result);
void Combination(char* string)

{
	
    if(string == NULL)
		
        return;
	
	
	
    int length = strlen(string);
	
    vector<char> result;
	
    for(int i = 1; i <= length; ++ i)
		
    {
		
        Combination(string, i, result);
		
    }
	
}



void Combination(char* string, int number, vector<char>& result)

{
	
    if(number == 0)
		
    {
		
        vector<char>::iterator iter = result.begin();
		
        for(; iter < result.end(); ++ iter)
			
            printf("%c", *iter);
		
        printf("\n");
		
		
		
        return;
		
    }
	
	
	
    if(*string == '\0')
		
        return;
	
	
	
//一个字符有两种选择

    result.push_back(*string);
	
    Combination(string + 1, number - 1, result);

    result.pop_back();	
    

    Combination(string + 1, number, result);
	
}

----------------------------------------------------------------------------

八皇后问题：col,row+col,row-col三个标记数组

// 8QUEEN.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream>
using namespace std;
const int SIZE = 8;
const int OFFSET = SIZE -1;
const int FLAT_SIZE = 3*SIZE-2;//2*(SIZE-1)+(SIZE-1)+1
int sov[SIZE];
bool hasa[FLAT_SIZE]={false};
bool hasb[FLAT_SIZE]={false};
bool hasc[SIZE]={false};
bool couldStand(int r,int c){
	
	return !hasc[c]&&!hasa[r+c+OFFSET]&&!hasb[r-c+OFFSET];
}
int m_count = 0;
void t(int r){
	
	
	for(int c=0;c<SIZE;c++){	
		
		if(couldStand(r,c)){
			sov[r]=c;
			hasa[r+c+OFFSET]=true;
			hasb[r-c+OFFSET]=true;
			hasc[c]=true;
			if(r==OFFSET){
				for(int i=0;i<SIZE;i++)
					printf("%d ",sov[i]+1);
				printf("\n");
				m_count++;
			}else t(r+1);
			hasa[r+c+OFFSET]=false;
			hasb[r-c+OFFSET]=false;
			hasc[c]=false;
		}
	}
	

}
int main(int argc, char* argv[])
{
	memset(hasc,false,sizeof(hasc));
	t(0);
	printf("Hello World %d!\n",m_count);
	return 0;
}