福州大学第十届校赛 & fzu 2128最长子串

来源：互联网发布：手机挖矿软件编辑：程序博客网时间：2024/06/05 06:01

思路：对于每个子串，求出母串中所有该子串的开始和结束位置，保存在 mark数组中，求完所有子串后，对mark数组按结束位置排序，然后用后一个的结束位置减去前一个的开始位置再减去 1，记录最大值
比如 aaaqwer 1 aaa 那么最长为 aaqwer

用strstr判断子串是否存在于母串中。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 1000005;struct MARK {int begin, end;bool operator <(const MARK& cmp) const {return end < cmp.end;}} mark[maxn];char s[maxn], t[1005][105];int n, cnt, next[105];void work(const char str[], const char sub[]) {//memset(next, 0, sizeof(next));//get_next(sub, next);int exp = 0, from, len = strlen(sub);while (strstr(str + exp, sub) != NULL) {from = strstr(str + exp, sub) - str;mark[cnt].begin = from;mark[cnt].end = from + len - 1;cnt++;exp = from + len - 1;}}int main() {while (scanf("%s", s) == 1) {scanf("%d", &n);for (int i = 0; i < n; i++)scanf("%s", t[i]);cnt = 0;for (int i = 0; i < n; i++) {work(s, t[i]);}mark[cnt].begin = mark[cnt].end = strlen(s);cnt++;sort(mark, mark + cnt);int ans = -1;for (int i = 0; i < cnt - 1; i++) {int len = mark[i + 1].end - mark[i].begin - 1;if (len > ans)ans = len;}printf("%d\n", ans == -1 ? strlen(s) : ans);}}

用KMP判断子串是否存在于母串中。

#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int maxn = 1000005;struct MARK {int begin, end;bool operator <(const MARK& cmp) const {return end < cmp.end;}} mark[maxn];char s[maxn], t[1005][105];int n, cnt, next[105];void get_next(const char *sub, int *next) {int len = strlen(sub);int i, k;next[0] = k = -1;for (i = 0; i < len;) {if (k == -1 || sub[i] == sub[k]) {k++;i++;if (sub[k] != sub[i])next[i] = k;elsenext[i] = next[k];} elsek = next[k];}}int KMP(const char *str, const char *sub, const int *next) {int i, j;int len1 = strlen(str), len2 = strlen(sub);for (i = 0, j = 0; i < len1 && j < len2;) {if (j == -1 || str[i] == sub[j]) {i++;j++;} elsej = next[j];}if (j == len2)return i - len2;return -1;}void work(const char str[], const char sub[]) {//memset(next, 0, sizeof(next));get_next(sub, next);int exp = 0, from = 0, len = strlen(sub);while ((from = KMP(str + exp, sub, next)) != -1) {mark[cnt].begin = from + exp;mark[cnt].end = from + exp + len - 1;cnt++;exp += from + len - (len == 1 ? 0 : 1);}}int main() {while (scanf("%s", s) == 1) {scanf("%d", &n);for (int i = 0; i < n; i++)scanf("%s", t[i]);cnt = 0;for (int i = 0; i < n; i++) {work(s, t[i]);}//for (int i = 0; i < cnt; i++)//printf("%d %d\n", mark[i].begin, mark[i].end);mark[cnt].begin = mark[cnt].end = strlen(s);cnt++;sort(mark, mark + cnt);int ans = -1;for (int i = 0; i < cnt - 1; i++) {int len = mark[i + 1].end - mark[i].begin - 1;if (len > ans)ans = len;}printf("%d\n", ans == -1 ? strlen(s) : ans);}}