最长公共子串 (输出子串)

题目链接：https://cn.vjudge.net/contest/318888#problem/I

题意：

求两个字符串的最长公共子串并且输出

思路：

和求最长公共子串的思路是一样的，就是多一个记录位置的操作。

  1 #include <stdio.h>
  2 #include <iostream>
  3 #include <algorithm>
  4 #include <string.h>
  5 #include <stdlib.h>
  6 #include <math.h>
  7 #include <queue>
  8 #include <set>
  9 
 10 #define INF 0x3f3f3f3f
 11 #define pii pair<int,int>
 12 #define LL long long
 13 using namespace std;
 14 typedef unsigned long long ull;
 15 const int MAXN = 200005;
 16 
 17 int wa[MAXN], wb[MAXN], wv[MAXN], ws_[MAXN];
 18 void Suffix(int *r, int *sa, int n, int m)
 19 {
 20     int i, j, k, *x = wa, *y = wb, *t;
 21     for(i = 0; i < m; ++i) ws_[i] = 0;
 22     for(i = 0; i < n; ++i) ws_[x[i] = r[i]]++;
 23     for(i = 1; i < m; ++i) ws_[i] += ws_[i - 1];
 24     for(i = n - 1; i >= 0; --i) sa[--ws_[x[i]]] = i;
 25     for(j = 1, k = 1; k < n; j *= 2, m = k)
 26     {
 27         for(k = 0, i = n - j; i < n; ++i) y[k++] = i;
 28         for(i = 0; i < n; ++i) if(sa[i] >= j) y[k++] = sa[i] - j;
 29         for(i = 0; i < n; ++i) wv[i] = x[y[i]];
 30         for(i = 0; i < m; ++i) ws_[i] = 0;
 31         for(i = 0; i < n; ++i) ws_[wv[i]]++;
 32         for(i = 1; i < m; ++i) ws_[i] += ws_[i - 1];
 33         for(i = n - 1; i >= 0; --i) sa[--ws_[wv[i]]] = y[i];
 34         t = x;
 35         x = y;
 36         y = t;
 37         for(x[sa[0]] = 0, i = k = 1; i < n; ++i)
 38             x[sa[i]] = (y[sa[i - 1]] == y[sa[i]] && y[sa[i - 1] + j] == y[sa[i] + j]) ? k - 1 : k++;
 39     }
 40 }
 41 int Rank[MAXN], height[MAXN], sa[MAXN], r[MAXN];
 42 void calheight(int *r,int *sa,int n)
 43 {
 44     int i,j,k=0;
 45     for(i=1; i<=n; i++)Rank[sa[i]]=i;
 46     for(i=0; i<n; height[Rank[i++]]=k)
 47         for(k?k--:0,j=sa[Rank[i]-1]; r[i+k]==r[j+k]; k++);
 48 }
 49 int n,minnum[MAXN][17];
 50 void RMQ()
 51 {
 52     int i,j;
 53     int m=(int)(log(n*1.0)/log(2.0));
 54     for(i=1;i<=n;i++)
 55         minnum[i][0]=height[i];
 56     for(j=1;j<=m;j++)
 57         for(i=1;i+(1<<j)-1<=n;i++)
 58             minnum[i][j]=min(minnum[i][j-1],minnum[i+(1<<(j-1))][j-1]);
 59 }
 60 int Ask_MIN(int a,int b)
 61 {
 62     int k=int(log(b-a+1.0)/log(2.0));
 63     return min(minnum[a][k],minnum[b-(1<<k)+1][k]);
 64 }
 65 int calprefix(int a,int b)
 66 {
 67     a=Rank[a],b=Rank[b];
 68     if(a>b)
 69         swap(a,b);
 70     return Ask_MIN(a+1,b);
 71 }
 72 char s[MAXN];
 73 int q[MAXN];
 74 int main()
 75 {
 76     int k;
 77     cin >> k;
 78     cin >> s;
 79     s[k] = ‘#‘;
 80     cin >> (s+k+1);
 81     int n = strlen(s);
 82     for (int i=0;i<n;i++){
 83         r[i] = s[i];
 84     }
 85     int maxx = 0;
 86     Suffix(r,sa,n+1,258);
 87     calheight(r,sa,n);
 88     int x,y;
 89     for (int i=1;i<=n;i++) {
 90         if (height[i] > maxx && 1ll * (sa[i] - k) * (sa[i - 1] - k) < 0){
 91             maxx = height[i];
 92             x = min(sa[i],sa[i-1]);
 93             y = x+maxx;
 94         }
 95     }
 96     for (int i=x;i<y;i++){
 97         printf("%c",s[i]);
 98     }
 99     return 0;
100 }