/**
* @param A, B: Two string.
* @return: the length of the longest common substring.
*/
int longestCommonSubstring(string &A, string &B) {
if (A.length() < B.length()) {
return longestCommonSubstring(B, A);
}
// table[i][j] means the longest length of common substring
// of A which ends with A[i - 1] and B which ends with B[j - 1].
vector<vector<int>> table(2, vector<int>(A.length() + 1, 0));
int longest = 0;
// if A[i - 1] != B[j - 1]:
// table[i][j] = 0
// if A[i - 1] == B[j - 1]:
// table[i][j] = table[i - 1][j - 1] + 1
for (int i = 1; i < A.length() + 1; ++i) {
for (int j = 1; j < B.length() + 1; ++j) {
if (A[i - 1] != B[j - 1]) {
table[i % 2][j] = 0;
} else {
table[i % 2][j] = table[(i - 1) % 2][j - 1] + 1;
longest = max(longest, table[i % 2][j]);
}
}
}
return longest;
}
/**
* @param A, B: Two string.
* @return: the length of the longest common substring.
*/
int longestCommonSubstring(string &A, string &B) {
// write your code here
if(A.length() > B.length()) return longestCommonSubstring(B, A);
vector<vector<int>> table(2, vector<int>(B.length()+1, 0));
int longest = 0;
for(int i = 1; i < A.length() + 1; ++i){
for(int j = 1; j < B.length() + 1; ++j){
if(A[i-1] == B[j-1]){
table[i%2][j] = table[(i-1)%2][j-1] + 1;
longest = max(longest, table[i%2][j]);
}else{
table[i%2][j] = 0;
}
}
}
return longest;
}
