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Posted on 2011-05-10 15:24 Uriel 阅读(636) 评论(0) 编辑 收藏 引用 所属分类: POJ 、 字符串处理
最近一直在准备省赛,基本都是复习算法和组队赛,基本没切什么题. 昨天想省赛前POJ刷到1200先,就跟光光对拍了下POJ过的题. 发现了这道字符串,顺便复习下KMP和后缀数组啥的.
这题跟POJ 3080基本完全一样,当年写过个解题报告 http://www.cppblog.com/Uriel/articles/98530.html
那时候还不会后缀数组,就用KMP和strstr两种方法水过去了. POJ 3450这题大概数据也不是很强吧...用KMP和strstr也都可以过的.
今天又试了下后缀数组,速度好慢... = =
后缀数组代码参考了 http://www.cnblogs.com/ltang/archive/2010/11/30/1891708.html
发现罗穗骞论文的代码里calheight那个函数数组下标那里可能会越界...,还请路过的大牛们指教.现在是照着上面那个Blog里的代码改了
各算法运行时间如下:
KMP: C++ 1469Ms
strstr: C++ 969Ms
Suffix Array (DA): C++ 1063Ms G++ 875Ms
Suffix Array (DC3): C++ 1063Ms
各算法的代码如下:
KMP
  /**//*
 * Problem: 3450 User: Uriel
* Memory: 8424K Time: 1469MS
* Language: C++ Result: Accepted
 */
 #include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<algorithm>
using namespace std;
int start, n, nxt[210];
char str[40010][210];
struct P  {
char res[210];
} Ans[4100];
char dest[100];
bool cmp(P a, P b) {
return strcmp(a.res, b.res) < 0;
}
void GetNext(char* str) {
nxt[0] = -1;
int i = 0, j = -1;
  while (str[i]) {
if (j == -1 || str[i] == str[j]) {
i++;
j++;
nxt[i] = j;
 } else
j = nxt[j];
}
}
int kmpMatch(char* Src, char* Dest) {
int i = 0, j = 0, s_len, p_len, sum = 0;
s_len = strlen(Src);
p_len = strlen(Dest);
M: while (i < s_len && j < p_len) {
if (j == -1 || Src[i] == Dest[j]) {
if (j == p_len - 1)
return i - p_len + 1;
i++;
j++;
} else
j = nxt[j];
}
return -1;
}
void Sov() {
int i;
for (i = 1; i < n; i++) {
if (kmpMatch(str[i], dest) == -1) {
start = 1;
return;
}
}
return;
}
int main() {
int i, j, k, s, len;
while (scanf("%d", &n), n) {
scanf("%d", &n);
memset(str, 0x00, sizeof(str));
for (i = 0; i < n; i++)
scanf("%s", str[i]);
len = strlen(str[0]);
s = 0;
for (i = len; i >= 1; i--) {
j = 0;
while (j + i <= len) {
start = 0;
memset(dest, 0x00, sizeof(dest));
strncpy(dest, &str[0][j], i);
GetNext(dest);
Sov();
if (!start) {
strcpy(Ans[s++].res, dest);
}
j++;
}
if (s)
break;
}
if (s) {
sort(Ans, Ans + s, cmp);
printf("%s\n", Ans[0].res);
} else {
puts("IDENTITY LOST");
}
}
return 0;
}
strstr
/**//*
* Problem: 3450 User: Uriel
* Memory: 8424K Time: 969MS
* Language: C++ Result: Accepted
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include<algorithm>
using namespace std;
int start, n;
char str[40010][210];
struct P {
char res[210];
} Ans[4100];
char dest[100];
int Next[100];
bool cmp(P a, P b) {
return strcmp(a.res, b.res) < 0;
}
void Sov() {
int i;
for (i = 1; i < n; i++) {
if (strstr(str[i], dest) == NULL) {
start = 1;
return;
}
}
return;
}
int main() {
int i, j, k, s, len;
while (scanf("%d", &n), n) {
scanf("%d", &n);
memset(str, 0x00, sizeof(str));
for (i = 0; i < n; i++)
scanf("%s", str[i]);
len = strlen(str[0]);
s = 0;
for (i = len; i >= 1; i--) {
j = 0;
while (j + i <= len) {
start = 0;
memset(dest, 0x00, sizeof(dest));
strncpy(dest, &str[0][j], i);
Sov();
if (!start) {
strcpy(Ans[s++].res, dest);
}
j++;
}
if (s)
break;
}
if (s) {
sort(Ans, Ans + s, cmp);
printf("%s\n", Ans[0].res);
} else {
puts("IDENTITY LOST");
}
}
return 0;
}
Suffix Array (DA)
/**//*
* Problem: 3450 User: Uriel
* Memory: 3604K Time: 875MS
* Language: G++ Result: Accepted
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define N 1000000
int n, r[N], sa[N];
int wa[N], wb[N], wv[N], ws[N];
int cmp(int *r, int a, int b, int l) {
return r[a] == r[b] && r[a + l] == r[b + l];
}
void da(int *r, int *sa, int n, int m) {
int i, j, p, *x = wa, *y = wb, *t;
for (i = 0; i < m; i++)
ws[i] = 0;
for (i = 0; i < n; i++)
ws[x[i] = r[i]]++;
for (i = 1; i < m; i++)
ws[i] += ws[i - 1];
for (i = n - 1; i >= 0; i--)
sa[--ws[x[i]]] = i;
for (j = 1, p = 1; p < n; j *= 2, m = p) {
for (p = 0, i = n - j; i < n; i++)
y[p++] = i;
for (i = 0; i < n; i++)
if (sa[i] >= j)
y[p++] = sa[i] - j;
for (i = 0; i < n; i++)
wv[i] = x[y[i]];
for (i = 0; i < m; i++)
ws[i] = 0;
for (i = 0; i < n; i++)
ws[wv[i]]++;
for (i = 1; i < m; i++)
ws[i] += ws[i - 1];
for (i = n - 1; i >= 0; i--)
sa[--ws[wv[i]]] = y[i];
for (t = x, x = y, y = t, p = 1, x[sa[0]] = 0, i = 1; i < n; i++)
x[sa[i]] = cmp(y, sa[i - 1], sa[i], j) ? p - 1 : p++;
}
return;
}
int rank[N], height[N];
void calheight(int *r) {
int i, j, k;
for (i = 0; i < n; i++)
rank[sa[i]] = i;
for (i = 0, height[0] = k = 0; i < n; height[rank[i++]] = k)
for (k ? k-- : 0, j = (rank[i] > 0) ? sa[rank[i] - 1] : 0; rank[i] > 0
&& r[i + k] == r[j + k]; k++)
;
}
int main() {
int m, t, i, j, sp, sb, se, mid, s, l, ans, c, w, ll;
char str[210];
bool visit[4010], isfind;
while (scanf("%d", &m), m) {
sp = 27;
for (j = n = 0; j < m; j++) {
scanf("%s", str);
for (i = 0; str[i]; i++) {
r[n++] = str[i] - 'a';
}
r[n++] = sp++;
}
ll = strlen(str);
da(r, sa, n, sp), calheight(r);
for (sb = 1, se = ll, mid = (sb + se) >> 1, s = 0, ans = -1; sb < se;) {
isfind = false;
for (int i = 0; (i < n) && !isfind; i++) {
if (height[i] < mid)
memset(visit, false, sizeof(visit)), t = 0;
if (height[i] >= mid) {
if (t == 0) {
l = sa[i - 1] / (ll + 1);
if (!visit[l])
visit[l] = true, t++;
}
l = sa[i] / (ll + 1);
if (!visit[l])
visit[l] = true, t++;
if (t == m)
isfind = true, ans = i;
}
}
if (isfind && mid == se)
break;
if (isfind)
(sb == mid && se > sb) ? (mid = se) : (sb = mid);
else
se = mid - 1, mid = (se + sb) >> 1;
}
if (ans != -1) {
for (int i = 0; i < mid; i++) {
c = r[sa[ans] + i];
putchar(c + 'a');
}
puts("");
} else
puts("IDENTITY LOST");
}
return 0;
}
Suffix Array (DC3)
/**//*
* Problem: 3450 User: Uriel
* Memory: 4084K Time: 1110MS
* Language: C++ Result: Accepted
*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#define N 1000000
#define F(x) ((x)/3+((x)%3==1?0:tb))
#define G(x) ((x)<tb?(x)*3+1:((x)-tb)*3+2)
int n, r[N * 3], sa[N * 3]; //注意数组大小
int wa[N], wb[N], wv[N], ws[N];
int c0(int *r, int a, int b) {
return r[a] == r[b] && r[a + 1] == r[b + 1] && r[a + 2] == r[b + 2];
}
int c12(int k, int *r, int a, int b) {
if (k == 2)
return r[a] < r[b] || r[a] == r[b] && c12(1, r, a + 1, b + 1);
else
return r[a] < r[b] || r[a] == r[b] && wv[a + 1] < wv[b + 1];
}
void sort(int *r, int *a, int *b, int n, int m) {
int i;
for (i = 0; i < n; ++i)
wv[i] = r[a[i]];
for (i = 0; i < m; ++i)
ws[i] = 0;
for (i = 0; i < n; ++i)
++ws[wv[i]];
for (i = 1; i < m; ++i)
ws[i] += ws[i - 1];
for (i = n - 1; i >= 0; --i)
b[--ws[wv[i]]] = a[i];
return;
}
void dc3(int *r, int *sa, int n, int m) {
int i, j, *rn = r + n, *san = sa + n, ta = 0, tb = (n + 1) / 3, tbc = 0, p;
r[n] = r[n + 1] = 0;
for (i = 0; i < n; ++i)
if (i % 3)
wa[tbc++] = i;
sort(r + 2, wa, wb, tbc, m);
sort(r + 1, wb, wa, tbc, m);
sort(r, wa, wb, tbc, m);
for (p = 1, rn[F(wb[0])] = 0, i = 1; i < tbc; ++i)
rn[F(wb[i])] = c0(r, wb[i - 1], wb[i]) ? p - 1 : p++;
if (p < tbc)
dc3(rn, san, tbc, p);
else
for (i = 0; i < tbc; ++i)
san[rn[i]] = i;
for (i = 0; i < tbc; ++i)
if (san[i] < tb)
wb[ta++] = san[i] * 3;
if (n % 3 == 1)
wb[ta++] = n - 1;
sort(r, wb, wa, ta, m);
for (i = 0; i < tbc; ++i)
wv[wb[i] = G(san[i])] = i;
for (i = 0, j = 0, p = 0; i < ta && j < tbc; ++p)
sa[p] = c12(wb[j] % 3, r, wa[i], wb[j]) ? wa[i++] : wb[j++];
for (; i < ta; ++p)
sa[p] = wa[i++];
for (; j < tbc; ++p)
sa[p] = wb[j++];
return;
}
int rank[N], height[N];
void calheight(int *r) {
int i, j, k;
for (i = 0; i < n; i++)
rank[sa[i]] = i;
for (i = 0, height[0] = k = 0; i < n; height[rank[i++]] = k)
for (k ? k-- : 0, j = (rank[i] > 0) ? sa[rank[i] - 1] : 0; rank[i] > 0
&& r[i + k] == r[j + k]; k++)
;
}
int main() {
int m, t, i, j, sp, sb, se, mid, s, l, ans, c, w, ll;
char str[210];
bool visit[4010], isfind;
while (scanf("%d", &m), m) {
sp = 27;
for (j = n = 0; j < m; j++) {
scanf("%s", str);
for (i = 0; str[i]; i++) {
r[n++] = str[i] - 'a';
}
r[n++] = sp++;
}
ll = strlen(str);
dc3(r, sa, n, sp), calheight(r);
for (sb = 1, se = ll, mid = (sb + se) >> 1, s = 0, ans = -1; sb < se;) {
isfind = false;
for (int i = 0; (i < n) && !isfind; i++) {
if (height[i] < mid)
memset(visit, false, sizeof(visit)), t = 0;
if (height[i] >= mid) {
if (t == 0) {
l = sa[i - 1] / (ll + 1);
if (!visit[l])
visit[l] = true, t++;
}
l = sa[i] / (ll + 1);
if (!visit[l])
visit[l] = true, t++;
if (t == m)
isfind = true, ans = i;
}
}
if (isfind && mid == se)
break;
if (isfind)
(sb == mid && se > sb) ? (mid = se) : (sb = mid);
else
se = mid - 1, mid = (se + sb) >> 1;
}
if (ans != -1) {
for (int i = 0; i < mid; i++) {
c = r[sa[ans] + i];
putchar(c + 'a');
}
puts("");
} else
puts("IDENTITY LOST");
}
return 0;
}
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