运用C++语言编程实现“顺序串”，并实现其上的基本操作。要求：（1）定长顺序串或堆式顺序串二选一；（2）实现串的创建（初始化）、清空、串的赋值、输出以及求子串、查找子串以及删除子串的操作；（3）查找子串的算法自选。

在C++中，我们可以选择使用定长顺序串（固定大小数组实现），因为这比较简单直观。下面是一个基础的实现示例：

#include <iostream>
using namespace std;

#define SIZE 10 // 定义串的最大长度

// 顺序串的结构体
struct SequenceString {
    char data[SIZE]; // 存储字符的数组
    int length; // 当前字符串的实际长度
};

// 初始化顺序串
SequenceString initSequenceString(const string& str) {
    SequenceString seq;
    seq.length = min(str.size(), SIZE);
    for (int i = 0; i < seq.length; ++i)
        seq.data[i] = str[i];
    return seq;
}

// 清空顺序串
void clear(SequenceString& seq) {
    seq.length = 0;
}

// 赋值操作
void assign(SequenceString& seq, const SequenceString& other) {
    if (seq.length + other.length > SIZE)
        throw "Overflow";
    for (int i = 0; i < other.length; ++i)
        seq.data[seq.length + i] = other.data[i];
    seq.length += other.length;
}

// 输出顺序串
void output(const SequenceString& seq) {
    for (int i = 0; i < seq.length; ++i)
        cout << seq.data[i];
    cout << endl;
}

// 求子串
SequenceString substr(const SequenceString& seq, int start, int end) {
    if (start < 0 || start >= seq.length || end > seq.length || start > end)
        throw "Invalid index";
    SequenceString sub;
    sub.length = end - start;
    for (int i = 0; i < sub.length; ++i)
        sub.data[i] = seq.data[start + i];
    return sub;
}

// 查找子串（例如使用KMP算法）
int findSubstring(const SequenceString& text, const SequenceString& pattern) {
    int n = text.length;
    int m = pattern.length;
    int kmpTable[m];
    buildKMP(pattern, kmpTable);

    int j = 0;
    for (int i = 0; i < n; ++i) {
        while (j > 0 && text.data[i] != pattern.data[j])
            j = kmpTable[j - 1];
        
        if (text.data[i] == pattern.data[j])
            j++;
        
        if (j == m)
            return i - m + 1;
    }

    return -1;
}

// KMP表构建函数
void buildKMP(const SequenceString& pattern, int* kmpTable) {
    kmpTable[0] = -1;
    int j = -1;
    for (int i = 1; i < pattern.length; ++i) {
        while (j > -1 && pattern.data[i] != pattern.data[j + 1])
            j = kmpTable[j];
        
        if (pattern.data[i] == pattern.data[j + 1]) 
            j++;
            
        kmpTable[i] = j;
    }
}