判断子序列、求最长公共子序列算法实现

电玩女神 2022-08-12 06:29 224阅读 0赞

#include<stdio.h>
    #include<string.h>
    #include<stdlib.h>
    
    #define FAIL 0
    #define SUCCESS 1
    
    //贪心法
    int getSubsequence(char P[], char T[])
    {
        int j = 0;
        int i;
        int m = strlen(P);
        int n = strlen(T);
        for (i = 0; i < m; i++)
        {
            //让P序列中的每一个字符和T序列中的字符进行比较
            while (P[i] != T[j])
            {
                j++;
                if (j == n)
                {
                    return FAIL;
                }
            }
            j++;
            if (j == n)
            {
                return FAIL;
            }
        }
        return SUCCESS;
    }
    
    //动态规划法
    void longestCommonSubsequence(char R[], char Q[])
    {
        int m = strlen(R);    //R序列的长度
        int n = strlen(Q);    //Q序列的长度
        char (*W)[m+1];       //W指向m+1个char值构成的数组
        W = (char (*)[m+1])malloc((n+1)*(m+1)*sizeof(int)); //动态申请n+1行m+1列的二维数组
        
        int i, j;
        for (i = 0; i <= m; i++)
        {
            W[0][i] = 0;     //将第一行置为0
        }
        for (j = 1; j <= n; j++)
        {
            W[j][0] = 0;   //将第一列置为0
        }
    
        for (i = 1; i <= m; i++)
        {
            for(j = 1; j <= n; j++)
            {
                if (R[i-1] == Q[j-1])
                {
                    W[i][j] = W[i-1][j-1] + 1;
                }
                else
                {
                    if (W[i][j-1] >= W[i-1][j])
                    {
                        W[i][j] = W[i][j-1];
                    }
                    else
                    {
                        W[i][j] = W[i-1][j];
                    }
                }
            }
        }
        
        //输出这个二维数组W
        for (i = 0; i <= m; i++)
        {
            for (j = 0; j <= n; j++)
            {
                printf("%d\t", W[i][j]);
            }
            printf("\n");
        }
    
        //逆序打印最大公共序列
        for (i = m, j = n; i >= 1 && j >= 1;)
        {
            if (R[i-1] == Q[j-1])
            {
                printf("%c ", R[i-1]);
                i--;
                j--;
            }
            else
            {
                if (W[i][j-1] > W[i-1][j])
                {
                    j--;
                }
                else
                {
                    i--;
                }
            }
        }
        free(W);
    }
    int main()
    {
        char P[] = "ACAB";
        char T[] = "ABCACABA";
    
       // P是T的子序列，当且仅当P中所有字符都以相同的顺序在T中出现
       if (getSubsequence(P, T))
       {
           puts("P是Q的子序列。");
       }
       else
       {
           puts("P不是Q的子序列。");
       }
       
       //最长公共子序列，X是Y的子序列，当且仅当X中的所有字符在Y中以相同的顺序出现
       char R[] = "ABBCADC";
       char Q[] = "BABBAC";
       longestCommonSubsequence(R, Q);   
       printf("\n");
     }

运行结果：

![SouthEast][]

[SouthEast]: /images/20220810/cf5b4b88e1ce47998957c95696ed6c4f.png