[516] C language brush LeetCode longest palindromic sequence (M)

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Given a string s, where to find the longest palindromic sequence. S may assume a maximum length of 1000.

Example 1:
Input:

"bbbab"
output:

4
a possible longest palindromic sequence is "bbbb".

Example 2:
Input:

"cbbd"
output:

2
a possible longest palindromic sequence is "bb".

Source: stay button (LeetCode)
link: https: //leetcode-cn.com/problems/longest-palindromic-subsequence
copyrighted by deduction from all networks. Commercial reprint please contact the authorized official, non-commercial reprint please indicate the source.

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Dynamic programming, dp [i] [j] represents the longest sequence since i to j, i began to pay attention to here from the last element, then the recurrence formula is:

dp [i] [j] = MAX (dp [i + 1] [j], dp [i] [j-1]); dp [i] [j] = dp [i + 1] [j-1] + 2; return value dp [0] [len-1]

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

int longestPalindromeSubseq(char * s){
    int len = strlen(s);
    int i, j;
    if (len == 0) return 0;
    int dp[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 (s[i] == s[j]) {
                dp[i][j] = dp[i+1][j-1] + 2;
            } else {
                dp[i][j] = MAX(dp[i+1][j], dp[i][j-1]);
            }
        }
    }
    
    return dp[0][len-1];
}