《剑指offer》第四十八题（最长不含重复字符的子字符串）

// 面试题48：最长不含重复字符的子字符串
// 题目：请从字符串中找出一个最长的不包含重复字符的子字符串，计算该最长子
// 字符串的长度。假设字符串中只包含从'a'到'z'的字符。

#include <string>
#include <iostream>

// 方法一：蛮力法
//不想说话

// 方法一：动态规划
int longestSubstringWithoutDuplication_2(const std::string& str)
{
    int curLength = 0;//记录当前长度
    int maxLength = 0;//记录最大长度

    int* position = new int[26];//检测26个字母上次出现在字符串下标，没有用过为-1
    for (int i = 0; i < 26; ++i)
        position[i] = -1;

    for (int i = 0; i < str.length(); ++i)
    {
        int prevIndex = position[str[i] - 'a'];
        if (prevIndex < 0 || i - prevIndex > curLength)//如果这个值之前没有被用过，或者用过但是二者相同字符的距离比当前记录的长度要大（这说明这个字符不再当前统计的范围内）
            ++curLength;
        else
        {
            if (curLength > maxLength)
                maxLength = curLength;

            curLength = i - prevIndex;//否则将二者相同字符的距离替换当前记录的长度
        }
        position[str[i] - 'a'] = i;//记录这个字符的位置为i
    }

    if (curLength > maxLength)//记录到结束了，要比较一下最后一段的长度是否是最长的
        maxLength = curLength;

    delete[] position;
    return maxLength;
}

// ====================测试代码====================
void testSolution2(const std::string& input, int expected)
{
    int output = longestSubstringWithoutDuplication_2(input);
    if (output == expected)
        std::cout << "Solution 2 passed, with input: " << input << std::endl;
    else
        std::cout << "Solution 2 FAILED, with input: " << input << std::endl;
}

void test(const std::string& input, int expected)
{
    testSolution2(input, expected);
}

void test1()
{
    const std::string input = "abcacfrar";
    int expected = 4;
    test(input, expected);
}

void test2()
{
    const std::string input = "acfrarabc";
    int expected = 4;
    test(input, expected);
}

void test3()
{
    const std::string input = "arabcacfr";
    int expected = 4;
    test(input, expected);
}

void test4()
{
    const std::string input = "aaaa";
    int expected = 1;
    test(input, expected);
}

void test5()
{
    const std::string input = "abcdefg";
    int expected = 7;
    test(input, expected);
}

void test6()
{
    const std::string input = "aaabbbccc";
    int expected = 2;
    test(input, expected);
}

void test7()
{
    const std::string input = "abcdcba";
    int expected = 4;
    test(input, expected);
}

void test8()
{
    const std::string input = "abcdaef";
    int expected = 6;
    test(input, expected);
}

void test9()
{
    const std::string input = "a";
    int expected = 1;
    test(input, expected);
}

void test10()
{
    const std::string input = "";
    int expected = 0;
    test(input, expected);
}

int main(int argc, char* argv[])
{
    test1();
    test2();
    test3();
    test4();
    test5();
    test6();
    test7();
    test8();
    test9();
    test10();
    system("pause");
    return 0;
}