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262 lines
6.4 KiB
262 lines
6.4 KiB
package class45;
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public class Code01_InsertS2MakeMostAlphabeticalOrder {
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// 暴力方法
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public static String right(String s1, String s2) {
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if (s1 == null || s1.length() == 0) {
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return s2;
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}
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if (s2 == null || s2.length() == 0) {
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return s1;
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}
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String p1 = s1 + s2;
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String p2 = s2 + s1;
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String ans = p1.compareTo(p2) > 0 ? p1 : p2;
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for (int end = 1; end < s1.length(); end++) {
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String cur = s1.substring(0, end) + s2 + s1.substring(end);
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if (cur.compareTo(ans) > 0) {
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ans = cur;
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}
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}
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return ans;
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}
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// 正式方法 O(N+M) + O(M^2)
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// N : s1长度
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// M : s2长度
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public static String maxCombine(String s1, String s2) {
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if (s1 == null || s1.length() == 0) {
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return s2;
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}
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if (s2 == null || s2.length() == 0) {
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return s1;
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}
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char[] str1 = s1.toCharArray();
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char[] str2 = s2.toCharArray();
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int N = str1.length;
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int M = str2.length;
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int min = str1[0];
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int max = str1[0];
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for (int i = 1; i < N; i++) {
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min = Math.min(min, str1[i]);
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max = Math.max(max, str1[i]);
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}
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for (int i = 0; i < M; i++) {
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min = Math.min(min, str2[i]);
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max = Math.max(max, str2[i]);
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}
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int[] all = new int[N + M + 1];
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int index = 0;
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for (int i = 0; i < N; i++) {
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all[index++] = str1[i] - min + 2;
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}
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all[index++] = 1;
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for (int i = 0; i < M; i++) {
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all[index++] = str2[i] - min + 2;
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}
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DC3 dc3 = new DC3(all, max - min + 2);
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int[] rank = dc3.rank;
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int comp = N + 1;
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for (int i = 0; i < N; i++) {
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if (rank[i] < rank[comp]) {
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int best = bestSplit(s1, s2, i);
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return s1.substring(0, best) + s2 + s1.substring(best);
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}
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}
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return s1 + s2;
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}
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public static int bestSplit(String s1, String s2, int first) {
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int N = s1.length();
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int M = s2.length();
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int end = N;
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for (int i = first, j = 0; i < N && j < M; i++, j++) {
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if (s1.charAt(i) < s2.charAt(j)) {
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end = i;
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break;
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}
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}
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String bestPrefix = s2;
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int bestSplit = first;
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for (int i = first + 1, j = M - 1; i <= end; i++, j--) {
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String curPrefix = s1.substring(first, i) + s2.substring(0, j);
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if (curPrefix.compareTo(bestPrefix) >= 0) {
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bestPrefix = curPrefix;
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bestSplit = i;
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}
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}
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return bestSplit;
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}
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public static class DC3 {
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public int[] sa;
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public int[] rank;
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public DC3(int[] nums, int max) {
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sa = sa(nums, max);
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rank = rank();
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}
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private int[] sa(int[] nums, int max) {
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int n = nums.length;
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int[] arr = new int[n + 3];
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for (int i = 0; i < n; i++) {
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arr[i] = nums[i];
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}
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return skew(arr, n, max);
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}
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private int[] skew(int[] nums, int n, int K) {
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int n0 = (n + 2) / 3, n1 = (n + 1) / 3, n2 = n / 3, n02 = n0 + n2;
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int[] s12 = new int[n02 + 3], sa12 = new int[n02 + 3];
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for (int i = 0, j = 0; i < n + (n0 - n1); ++i) {
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if (0 != i % 3) {
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s12[j++] = i;
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}
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}
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radixPass(nums, s12, sa12, 2, n02, K);
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radixPass(nums, sa12, s12, 1, n02, K);
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radixPass(nums, s12, sa12, 0, n02, K);
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int name = 0, c0 = -1, c1 = -1, c2 = -1;
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for (int i = 0; i < n02; ++i) {
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if (c0 != nums[sa12[i]] || c1 != nums[sa12[i] + 1] || c2 != nums[sa12[i] + 2]) {
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name++;
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c0 = nums[sa12[i]];
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c1 = nums[sa12[i] + 1];
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c2 = nums[sa12[i] + 2];
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}
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if (1 == sa12[i] % 3) {
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s12[sa12[i] / 3] = name;
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} else {
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s12[sa12[i] / 3 + n0] = name;
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}
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}
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if (name < n02) {
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sa12 = skew(s12, n02, name);
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for (int i = 0; i < n02; i++) {
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s12[sa12[i]] = i + 1;
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}
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} else {
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for (int i = 0; i < n02; i++) {
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sa12[s12[i] - 1] = i;
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}
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}
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int[] s0 = new int[n0], sa0 = new int[n0];
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for (int i = 0, j = 0; i < n02; i++) {
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if (sa12[i] < n0) {
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s0[j++] = 3 * sa12[i];
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}
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}
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radixPass(nums, s0, sa0, 0, n0, K);
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int[] sa = new int[n];
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for (int p = 0, t = n0 - n1, k = 0; k < n; k++) {
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int i = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
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int j = sa0[p];
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if (sa12[t] < n0 ? leq(nums[i], s12[sa12[t] + n0], nums[j], s12[j / 3])
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: leq(nums[i], nums[i + 1], s12[sa12[t] - n0 + 1], nums[j], nums[j + 1], s12[j / 3 + n0])) {
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sa[k] = i;
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t++;
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if (t == n02) {
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for (k++; p < n0; p++, k++) {
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sa[k] = sa0[p];
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}
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}
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} else {
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sa[k] = j;
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p++;
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if (p == n0) {
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for (k++; t < n02; t++, k++) {
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sa[k] = sa12[t] < n0 ? sa12[t] * 3 + 1 : (sa12[t] - n0) * 3 + 2;
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}
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}
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}
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}
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return sa;
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}
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private void radixPass(int[] nums, int[] input, int[] output, int offset, int n, int k) {
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int[] cnt = new int[k + 1];
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for (int i = 0; i < n; ++i) {
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cnt[nums[input[i] + offset]]++;
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}
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for (int i = 0, sum = 0; i < cnt.length; ++i) {
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int t = cnt[i];
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cnt[i] = sum;
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sum += t;
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}
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for (int i = 0; i < n; ++i) {
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output[cnt[nums[input[i] + offset]]++] = input[i];
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}
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}
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private boolean leq(int a1, int a2, int b1, int b2) {
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return a1 < b1 || (a1 == b1 && a2 <= b2);
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}
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private boolean leq(int a1, int a2, int a3, int b1, int b2, int b3) {
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return a1 < b1 || (a1 == b1 && leq(a2, a3, b2, b3));
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}
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private int[] rank() {
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int n = sa.length;
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int[] ans = new int[n];
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for (int i = 0; i < n; i++) {
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ans[sa[i]] = i;
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}
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return ans;
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}
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}
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// for test
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public static String randomNumberString(int len, int range) {
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char[] str = new char[len];
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for (int i = 0; i < len; i++) {
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str[i] = (char) ((int) (Math.random() * range) + '0');
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}
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return String.valueOf(str);
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}
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// for test
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public static void main(String[] args) {
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int range = 10;
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int len = 50;
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int testTime = 100000;
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System.out.println("功能测试开始");
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for (int i = 0; i < testTime; i++) {
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int s1Len = (int) (Math.random() * len);
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int s2Len = (int) (Math.random() * len);
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String s1 = randomNumberString(s1Len, range);
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String s2 = randomNumberString(s2Len, range);
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String ans1 = right(s1, s2);
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String ans2 = maxCombine(s1, s2);
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if (!ans1.equals(ans2)) {
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System.out.println("Oops!");
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System.out.println(s1);
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System.out.println(s2);
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System.out.println(ans1);
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System.out.println(ans2);
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break;
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}
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}
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System.out.println("功能测试结束");
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System.out.println("==========");
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System.out.println("性能测试开始");
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int s1Len = 1000000;
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int s2Len = 500;
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String s1 = randomNumberString(s1Len, range);
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String s2 = randomNumberString(s2Len, range);
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long start = System.currentTimeMillis();
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maxCombine(s1, s2);
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long end = System.currentTimeMillis();
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System.out.println("运行时间 : " + (end - start) + " ms");
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System.out.println("性能测试结束");
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}
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}
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