经典DP，想了很久，开始想复杂了。

#include 
     
      using namespace std;#define MAXNUM 100int mymax(int a, int b) {    return (a>b) ? a:b;}int main() {    int case_n;    int a_n, b_n;    int i, j;    int a[MAXNUM], b[MAXNUM];    int match[MAXNUM][MAXNUM];    int max_a2b[MAXNUM][MAXNUM], max_b2a[MAXNUM][MAXNUM];    cin >>case_n;    while (case_n--) {        cin >>a_n>>b_n;        for (i=1; i<=a_n; ++i)            cin >>a[i];        for (i=1; i<=b_n; ++i)            cin >>b[i];        for (i=0; i<=a_n; ++i) {            match[i][0] = 0;            max_a2b[i][0] = 0;        }        for (i=0; i<=b_n; ++i) {            match[0][i] = 0;            max_b2a[i][0] = 0;        }        for (i=1; i<=a_n; ++i)            for (j=1; j<=b_n; ++j) {                if (a[i] == b[j-1])                    max_a2b[i][j] = j-1;                else                    max_a2b[i][j] = max_a2b[i][j-1];            }        for (i=1; i<=b_n; ++i)            for (j=1; j<=a_n; ++j) {                if (b[i] == a[j-1])                    max_b2a[i][j] = j-1;                else                    max_b2a[i][j] = max_b2a[i][j-1];            }        int pos_b, pos_a;        for (i=1; i<=a_n; ++i) {            for (j=1; j<=b_n; ++j) {                match[i][j] = mymax(match[i-1][j], match[i][j-1]);                pos_b = max_a2b[i][j];                pos_a = max_b2a[j][i];                if (pos_b>0 && pos_a>0 && a[i] != b[j]) {                    match[i][j] = mymax(match[i][j], match[pos_a-1][pos_b-1]+2);                }            }        }        cout <
      
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