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66 lines
1.6 KiB
66 lines
1.6 KiB
package class15;
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//leetcode 188
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public class Code04_BestTimeToBuyAndSellStockIV {
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public static int maxProfit(int K, int[] prices) {
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if (prices == null || prices.length == 0) {
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return 0;
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}
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int N = prices.length;
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if (K >= N / 2) {
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return allTrans(prices);
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}
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int[][] dp = new int[K + 1][N];
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int ans = 0;
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for (int tran = 1; tran <= K; tran++) {
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int pre = dp[tran][0];
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int best = pre - prices[0];
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for (int index = 1; index < N; index++) {
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pre = dp[tran - 1][index];
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dp[tran][index] = Math.max(dp[tran][index - 1], prices[index] + best);
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best = Math.max(best, pre - prices[index]);
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ans = Math.max(dp[tran][index], ans);
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}
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}
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return ans;
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}
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public static int allTrans(int[] prices) {
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int ans = 0;
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for (int i = 1; i < prices.length; i++) {
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ans += Math.max(prices[i] - prices[i - 1], 0);
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}
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return ans;
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}
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// 课上写的版本，对了
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public static int maxProfit2(int K, int[] arr) {
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if (arr == null || arr.length == 0 || K < 1) {
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return 0;
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}
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int N = arr.length;
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if (K >= N / 2) {
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return allTrans(arr);
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}
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int[][] dp = new int[N][K + 1];
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// dp[...][0] = 0
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// dp[0][...] = arr[0.0] 0
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for (int j = 1; j <= K; j++) {
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// dp[1][j]
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int p1 = dp[0][j];
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int best = Math.max(dp[1][j - 1] - arr[1], dp[0][j - 1] - arr[0]);
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dp[1][j] = Math.max(p1, best + arr[1]);
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// dp[1][j] 准备好一些枚举，接下来准备好的枚举
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for (int i = 2; i < N; i++) {
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p1 = dp[i - 1][j];
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int newP = dp[i][j - 1] - arr[i];
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best = Math.max(newP, best);
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dp[i][j] = Math.max(p1, best + arr[i]);
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}
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}
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return dp[N - 1][K];
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}
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}
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