完成串

ch4/sequence_static.cpp

@@ -0,0 +1,154 @@
+#include <stdio.h>
+#define MAXLEN 255
+typedef struct
+{
+    char ch[MAXLEN];
+    int length;
+} SString;
+
+void InitString(SString &S)
+{
+    S.length = 0;
+}
+
+// 求串长
+int StrLength(SString S)
+{
+    return S.length;
+}
+
+// 求子串
+bool SubString(SString &Sub, SString S, int pos, int len)
+{
+    // 子串范围越界
+    if (pos + len - 1 > S.length)
+    {
+        return false;
+    }
+    for (int i = pos; i < pos + len; i++)
+    {
+        Sub.ch[i - pos + 1] = S.ch[i];
+    }
+    Sub.length = len;
+    return true;
+}
+
+// 比较操作
+int StrCompare(SString S, SString T)
+{
+    for (int i = 1; i <= S.length && i <= T.length; i++)
+    {
+        if (S.ch[i] != T.ch[i])
+        {
+            return S.ch[i] - T.ch[i];
+        }
+    }
+    // 扫描过所有字符都相同，则长度长的串更大
+    return S.length - T.length;
+}
+
+// 定位操作
+int Index(SString S, SString T)
+{
+    int i = 1, n = StrLength(S), m = StrLength(T);
+    SString sub;
+    while (i <= n - m + 1)
+    {
+        SubString(sub, S, i, m);
+        if (StrCompare(sub, T) != 0)
+        {
+            ++i;
+        }
+        else
+        {
+            return i;
+        }
+    }
+    return 0;
+}
+
+// 定位操作
+int Index2(SString S, SString T)
+{
+    int k = 1; // 记录主串中的匹配开始位置
+    int i = k, j = 1;
+    while (i <= S.length && j <= T.length)
+    {
+        if (S.ch[i] == T.ch[j])
+        {
+            ++i;
+            ++j;
+        }
+        else
+        {
+            k++;
+            i = k;
+            j = 1;
+        }
+    }
+    if (j > T.length)
+    {
+        return k;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+// 求模式串 T 的 next 数组
+void get_next(SString T, int next[])
+{
+    int i = 1, j = 0;
+    next[1] = 0;
+    while (i < T.length)
+    {
+        if (j == 0 || T.ch[i] == T.ch[j])
+        {
+            ++i;
+            ++j;
+            // 若 pi=pj，则 next[j+1]=next[j]+1
+            next[i] = j;
+        }
+        else
+        {
+            // 否则令 j=next[j]，循环继续
+            j = next[j];
+        }
+    }
+}
+
+// KMP 算法
+int Index_KMP(SString S, SString T)
+{
+    int i = 1, j = 1;
+    int next[T.length + 1];
+    get_next(T, next); // 时间复杂度：$O(m)$
+    while (i <= S.length && j <= T.length) // 时间复杂度：$O(n)$
+    {
+        if (j == 0 || S.ch[i] == T.ch[j])
+        {
+            ++i;
+            ++j;
+        }
+        else
+        {
+            j = next[j];
+        }
+    }
+    if (j > T.length)
+    {
+        return i - T.length;
+    }
+    else
+    {
+        return 0;
+    }
+}
+
+int main(int argc, char const *argv[])
+{
+    SString S;
+    InitString(S);
+    return 0;
+}