05_最长回文子序列长度

 一、测试输入：

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二、经转移公式推导： 

 三、测试程序

/*
 *    最长回文子系列
 *
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAX(a, b)    (a)>(b) ? (a):(b)

int get_lps_len(unsigned char *str)
{
    unsigned int len = 0;
    int i = 0;
    int j = 0;

    len = strlen(str);
    int (*dp)[len] = (int (*)[len])malloc(sizeof(int)*len*len);
    memset(dp, 0, sizeof(int)*len*len);

    for (i=len-1; i>=0; i--) {
        dp[i][i] = 1;
        for (j=i+1; j<len; j++) {
            if (str[i] == str[j])
                dp[i][j] = dp[i+1][j-1] + 2;
            else
                dp[i][j] = MAX(dp[i+1][j], dp[i][j-1]);
        }
    }

    for (i=0; i<len; i++) {
        for (j=0; j<len; j++)
            printf("%d ", dp[i][j]);
        puts("");
    }

    len = dp[0][len-1];
    free(dp);

    return len;
}

int main()
{
    unsigned char str[1024] = {0};
    
    while (~scanf("%s", str))
        printf("%d
", get_lps_len(str));

    return 0;
}