hdu 4513 吉哥系列故事——完美队形II

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题目给出的整数哦, 不过也完全可以通过manacher算法来实现查找最长的回文哦.

这个道题比平常的回文长度的题目加多一个判断而已啦.

#include <stdio.h>#include <string.h>#define MAX 100005#define min(a, b) (a > b ? b : a)int q[MAX], newQ[MAX*2];int p[MAX*2];int main() {int T, n, m;int mx, maxLen, id;int i, z;int a, b;while (scanf("%d", &T) != EOF) {while (T--) {memset(newQ, 0, sizeof(newQ));scanf("%d", &n);for (i = 1; i <= n; i++) {scanf("%d", &q[i]);}m = 2*n;newQ[0] = -1, newQ[1] = 0;for (i = 1; i <= n; i++) {newQ[i*2] = q[i]; newQ[i*2 + 1] = 0;}mx = maxLen = id = 0;for (i = 1; i <= m; i++) {if (mx > i) {p[i] = min(p[id*2 - i], mx - i);} else {p[i] = 1;}while (newQ[i - p[i]] == newQ[i + p[i]]) {if (newQ[i + p[i]] == 0) {p[i]++;} else {a = i - p[i];b = i + p[i];if (newQ[a] <= newQ[a + 2] && newQ[b - 2] >= newQ[b]) {p[i]++;continue ;} break ;}}if (p[i] + i > mx) {mx = p[i] + i;id = i;}if (maxLen < p[i]) {maxLen = p[i];}}printf("%d\n", maxLen - 1);}}return 0;}