穷举排列组合算法

最新推荐文章于 2022-03-04 11:46:54 发布

转载最新推荐文章于 2022-03-04 11:46:54 发布 · 940 阅读

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原文链接：http://www.cnblogs.com/PJXWang/p/5231464.html

本文介绍了一个使用C语言实现的暴力破解算法，该算法通过遍历指定字符集的所有可能组合来生成字符串。文章详细展示了如何递归地构建不同长度的字符串，并在达到最大长度时输出结果。

// main.m

// test

// Created by mac on 16-3-1.

#import <Foundation/Foundation.h>

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

static const char alphabet[] =

"abcdefghijklmnopqrstuvwxyz"

"ABCDEFGHIJKLMNOPQRSTUVWXYZ"

"0123456789";

static const int alphabetSize = sizeof(alphabet) - 1;

void bruteImpl(char* str, int index, int maxDepth)

{

for (int i = 0; i < alphabetSize; ++i)

{

str[index] = alphabet[i];

if (index == maxDepth - 1) printf("%s\n", str);

else bruteImpl(str, index + 1, maxDepth);

}

void bruteSequential(int maxLen)

{

char* buf = malloc(maxLen + 1);

for (int i = 1; i <= maxLen; ++i)

{

memset(buf, 0, maxLen + 1);

bruteImpl(buf, 0, i);

}

free(buf);

}

static const int BUFFLEN=1024*100;

void brute2(int maxLen)
{
    char* indices = malloc(maxLen + 1);
    char* terminal = indices+maxLen;
    char *printbuff = malloc(BUFFLEN);
    char *pbend = &printbuff[BUFFLEN-1];
    char *b = printbuff;
    *pbend = '\0';
    ++indices[0];
    char *p;

    while (*terminal == 0) {
        // print value
        for (p = indices; *p; ++p)
            ;
        for (--p ; p >= indices; --p) {
            *b++ = alphabet[*p-1];
            if (b == pbend) {
                fwrite(printbuff, 1, b-printbuff, stdout);
                b = printbuff;
            }
        }
        *b++ = '\n';
        if (b == pbend) {
            fwrite(printbuff, 1, b-printbuff, stdout);
            b = printbuff;
        }
        // increment values
        int carry = 1;
        for (++p ; carry; ++p)