poj 2774 Long Long Message(后缀数组)
题意:给定两个字符串A 和B。求最长公共子串。
思路:将两个字符串连接起来中间用一个没出现过的符号切割。
所以答案为满足后缀在不同的串中且height值最大的height值
#include<cstdio> #include<cstring> #include<cmath> #include<cstdlib> #include<iostream> #include<algorithm> #include<vector> #include<map> #include<queue> #include<stack> #include<string> #include<map> #include<set> #define eps 1e-6 #define LL long long using namespace std; const int maxn = 200000 + 200; //const int INF = 0x3f3f3f3f; char str1[100010], str2[100010]; struct SuffixArray { int s[maxn]; /// 原始字符数组(最后一个字符应必须是0,而前面的字符必须非0) int sa[maxn]; // 后缀数组,sa[0]一定是n-1,即最后一个字符 int rank[maxn]; // 名次数组 int height[maxn]; // height数组 int t[maxn], t2[maxn], c[maxn]; // 辅助数组 int n; // 字符个数 void clear() { n = 0; memset(sa, 0, sizeof(sa)); } /// m为最大字符值加1。!!! 调用之前需设置好s和n void build_sa(int m) { int i, *x = t, *y = t2; for(i = 0; i < m; i++) c[i] = 0; for(i = 0; i < n; i++) c[x[i] = s[i]]++; for(i = 1; i < m; i++) c[i] += c[i-1]; for(i = n-1; i >= 0; i--) sa[--c[x[i]]] = i; for(int k = 1; k <= n; k <<= 1) { int p = 0; for(i = n-k; i < n; i++) y[p++] = i; for(i = 0; i < n; i++) if(sa[i] >= k) y[p++] = sa[i]-k; for(i = 0; i < m; i++) c[i] = 0; for(i = 0; i < n; i++) c[x[y[i]]]++; for(i = 0; i < m; i++) c[i] += c[i-1]; for(i = n-1; i >= 0; i--) sa[--c[x[y[i]]]] = y[i]; swap(x, y); p = 1; x[sa[0]] = 0; for(i = 1; i < n; i++) x[sa[i]] = y[sa[i-1]]==y[sa[i]] && y[sa[i-1]+k]==y[sa[i]+k] ? p-1 : p++; if(p >= n) break; m = p; } } void build_height() { int i, j, k = 0; for(i = 0; i < n; i++) rank[sa[i]] = i; for(i = 0; i < n; i++) { if(k) k--; j = sa[rank[i]-1]; while(s[i+k] == s[j+k]) k++; height[rank[i]] = k; } } } sa; void init() { sa.clear(); int len1 = strlen(str1), len2 = strlen(str2); for(int i = 0; i < len1; i++) sa.s[i] = str1[i] - 'a' + 1; for(int i = 0; i < len2; i++) sa.s[len1+i+1] = str2[i] - 'a' + 1; sa.s[len1] = 27; sa.s[len1+len2+1] = 0; sa.n = len1 + len2 + 2; sa.build_sa(30); sa.build_height(); } void solve() { int ans = 0; int len1 = strlen(str1); for(int i = 1; i < sa.n; i++) { if(sa.height[i] > ans) if(sa.sa[i-1]<len1&&sa.sa[i]>len1 || sa.sa[i]<len1&&sa.sa[i-1]>len1) ans = sa.height[i]; } cout << ans << endl; } int main() { //freopen("input.txt", "r", stdin); while(scanf("%s%s", str1, str2) == 2) { init(); solve(); } return 0; }