UV 12338, uva12338

UV 12338, uva12338
Ultraviolet A 12338-Anti-Rhyme Pairs

Question Link

Given some strings, obtain the length of the longest common prefix of the two strings each time.

Train of Thought: sort the strings to find the array of height and rank, and then use RMQ to query

Code:

#include <cstdio>#include <cstring>#include <iostream>#include <string>#include <algorithm>using namespace std;const int N = 100005;typedef pair<string, int> pii;pii str[N];int save[N];int t, n, height[N], rank[N];void init() {    scanf("%d", &n);    for (int i = 0; i < n; i++) {cin >> str[i].first;save[i] = str[i].first.length();str[i].second = i;    }    sort(str, str + n);    for (int i = 0; i < n; i++) {rank[str[i].second] = i;if (i == 0) continue;int len = min(str[i - 1].first.length(), str[i].first.length());int j;for (j = 0; j < len; j++) {    if (str[i - 1].first[j] != str[i].first[j])break;}height[i] = j;    }}int best[N * 10][20];void initRMQ() {    for (int i = 0; i < n; i++) best[i][0] = height[i];    for (int j = 1; (1<<j) <= n; j++)for (int i = 0; i + (1<<j) - 1 < n; i++)    best[i][j] = min(best[i][j - 1], best[i + (1<<(j - 1))][j - 1]);}int lcp(int L, int R) {    L--; R--;    if (L == R) return save[L];    L = rank[L]; R = rank[R];    if (L > R) swap(L, R);    L++;    int k = 0;    while ((1<<(k + 1)) <= R - L + 1) k++;    return min(best[L][k], best[R - (1<<k) + 1][k]);}int main() {    int cas = 0;    scanf("%d", &t);    while (t--) {init();initRMQ();int q, l, r;scanf("%d", &q);printf("Case %d:\n", ++cas);while (q--) {    scanf("%d%d", &l, &r);    printf("%d\n", lcp(l, r));}    }    return 0;}