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package class03;
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import java.util.ArrayList;
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import java.util.HashMap;
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// 本题测试链接 : https://leetcode.com/problems/freedom-trail/
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public class Code07_FreedomTrail {
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public static int findRotateSteps(String r, String k) {
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char[] ring = r.toCharArray();
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int N = ring.length;
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HashMap<Character, ArrayList<Integer>> map = new HashMap<>();
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for (int i = 0; i < N; i++) {
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if (!map.containsKey(ring[i])) {
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map.put(ring[i], new ArrayList<>());
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}
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map.get(ring[i]).add(i);
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}
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char[] str = k.toCharArray();
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int M = str.length;
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int[][] dp = new int[N][M + 1];
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// hashmap
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// dp[][] == -1 : 表示没算过！
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for (int i = 0; i < N; i++) {
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for (int j = 0; j <= M; j++) {
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dp[i][j] = -1;
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}
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}
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return process(0, 0, str, map, N, dp);
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}
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// 电话里：指针指着的上一个按键preButton
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// 目标里：此时要搞定哪个字符？keyIndex
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// map : key 一种字符 value: 哪些位置拥有这个字符
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// N: 电话大小
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// f(0, 0, aim, map, N)
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public static int process(int preButton, int index, char[] str, HashMap<Character, ArrayList<Integer>> map, int N,
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int[][] dp) {
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if (dp[preButton][index] != -1) {
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return dp[preButton][index];
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}
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int ans = Integer.MAX_VALUE;
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if (index == str.length) {
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ans = 0;
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} else {
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// 还有字符需要搞定呢！
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char cur = str[index];
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ArrayList<Integer> nextPositions = map.get(cur);
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for (int next : nextPositions) {
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int cost = dial(preButton, next, N) + 1 + process(next, index + 1, str, map, N, dp);
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ans = Math.min(ans, cost);
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}
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}
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dp[preButton][index] = ans;
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return ans;
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}
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public static int dial(int i1, int i2, int size) {
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return Math.min(Math.abs(i1 - i2), Math.min(i1, i2) + size - Math.max(i1, i2));
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}
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}
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