1. source codes

#include <iostream> using namespace std; typedef enum { LR = 0, UP = 1, LEFT = 2 }DIRECTION; void printLCS(DIRECTION *b, char *X, int i, int j, int n) { if (i == 0|| j == 0) { return; } if (b[i * n + j] == LR) { printLCS(b, X, i - 1, j - 1, n); cout << X[i - 1]<< " "; } else { if (b[i * n + j] == UP) { printLCS(b, X, i - 1, j, n); } else { printLCS(b, X, i, j - 1, n); } } } /* * A: char sequence * B: char sequence * la: length of char sequence A * lb: length of char sequence B */ void longestCommonSequence(char* A, int la, char* B, int lb) { int m = la; int n = lb; int *c = new int[m * n]; DIRECTION *b = new DIRECTION[m * n]; for (int i = 0; i < m; i++) { for (int j = 0; j < n; j++) { c[i * n + j] = 0; } } for (int i = 1; i < m; i++) { for (int j = 1; j < n; j++) { if (A[i - 1] == B[j - 1]) { c[i * n + j] = c[(i - 1) * n + (j - 1)] + 1; b[i * n + j] = LR; } else { if (c[(i - 1) * n + j] >= c[i * n + (j - 1)]) { c[i * n + j] = c[(i - 1) * n + j]; b[i * n + j] = UP; } else { c[i * n + j] = c[i * n + (j - 1)]; b[i * n + j] = LEFT; } } } } cout << "matrix c:"<< endl; for (int i = 0; i < m; i++) { for (int j = 0; j < n; j++) { cout << c[ i * n + j]<< " "; } cout << endl; } cout << endl; cout << "matrix b:"<< endl; for (int i = 0; i < m; i++) { for (int j = 0; j < n; j++) { if (b[i * n + j] == LR) { cout << "//"; } else { if (b[i * n + j] == UP) { cout << "|"; } else { cout << "-"; } } cout << " "; } cout << endl; } cout << endl; cout << "one of LCS is : "; printLCS(b, A, m - 1, n - 1, n); } int main() { char A[] = { 'A', 'B', 'C', 'B', 'D', 'A', 'B' }; char B[] = { 'B', 'D', 'C', 'A', 'B', 'A' }; int la = sizeof(A)/sizeof(char); int lb = sizeof(B)/sizeof(char); longestCommonSequence(A, la + 1, B, lb + 1); }

2. test result

matrix c: 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 1 1 1 1 2 2 0 1 1 2 2 2 2 0 1 1 2 2 3 3 0 1 2 2 2 3 3 0 1 2 2 3 3 4 0 1 2 2 3 4 4 matrix b: / / / / / / / / | | | / - / / / - - | / - / | | / - | | / / | | | / - / | / | | | | / | | | / | / / / | | | / | one of LCS is : B C B A