DP

股票问题

Author: h2pl

src/DP/其他问题如股票/买入和售出股票最大的收益.java

@@ -4,4 +4,58 @@
  * Created by 周杰伦 on 2018/4/9.
  */
 public class 买入和售出股票最大的收益 {
+    public static void main(String[] args) {
+        int []a = {7, 1, 5, 3, 6, 4};
+        int []b = {3,2,6,5,0,3};
+        System.out.println(maxProfit(a));
+        System.out.println(maxProfit(b));
+
+    }
+    public static int maxProfit(int[] prices) {
+        if (prices.length <= 1) {
+            return 0;
+        }
+        int maxProfit = 0;
+        int lowest = Integer.MAX_VALUE;
+        for (int v : prices) {
+            lowest = Math.min(v, lowest);
+            maxProfit = Math.max(maxProfit, v - lowest);
+        }
+        return maxProfit;
+    }
+    //时间复杂度过大
+//    public static int maxProfit(int[] prices) {
+//        int max = 0;
+//        for (int i = 1;i < prices.length;i ++) {
+//            for (int j = 0;j < i;j ++) {
+//                if (prices[i] - prices[j] > max)max = prices[i] - prices[j];
+//            }
+//        }
+//        return max;
+//    }
+
+    //解法太复杂
+//    public static int maxProfit(int[] prices) {
+//        if (prices.length == 0)return 0;
+//        int []dp = new int[prices.length];
+//        dp[0] = 0;
+//        int []mins = new int[prices.length];
+//        mins[0] = prices[0];
+//        for (int i = 1;i < prices.length;i ++) {
+//            if (prices[i] < mins[i - 1]) {
+//                mins[i] = prices[i];
+//            }else {
+//                mins[i] = mins[i - 1];
+//            }
+//        }
+//        for (int i = 1;i < prices.length;i ++) {
+//            int min = mins[i];
+//            if (prices[i] > min && prices[i] > prices[i - 1]) {
+//                dp[i] = Math.max(prices[i] - min, dp[i - 1]);
+//            }else {
+//                dp[i] = dp[i - 1];
+//            }
+//        }
+//        return dp[prices.length - 1];
+//    }
 }

src/DP/其他问题如股票/需要交易费用的股票交易_多数组.java

@@ -0,0 +1,34 @@
+package DP.其他问题如股票;
+
+/**
+ * Created by 周杰伦 on 2018/4/10.
+ */
+public class 需要交易费用的股票交易_多数组 {
+    public int maxProfit(int[] prices, int fee) {
+        if(prices.length <= 1) return 0;
+        int[] buy = new int[prices.length];
+        int[] hold = new int[prices.length];
+        int[] skip = new int[prices.length];
+        int[] sell = new int[prices.length];
+        // the moment we buy a stock, our balance should decrease
+        buy[0] = 0 - prices[0];
+        // assume if we have stock in the first day, we are still in deficit
+        hold[0] = 0 - prices[0];
+        for(int i = 1; i < prices.length; i++){
+            // We can only buy on today if we sold stock
+            // or skipped with empty portfolio yesterday
+            buy[i] = Math.max(skip[i-1], sell[i-1]) - prices[i];
+            // Can only hold if we bought or already holding stock yesterday
+            hold[i] = Math.max(buy[i-1], hold[i-1]);
+            // Can skip only if we skipped, or sold stock yesterday
+            skip[i] = Math.max(skip[i-1], sell[i-1]);
+            // Can sell only if we bought, or held stock yesterday
+            sell[i] = Math.max(buy[i-1], hold[i-1]) + prices[i] - fee;
+        }
+        // Get the max of all the 4 actions on the last day.
+        int max = Math.max(buy[prices.length - 1], hold[prices.length - 1]);
+        max = Math.max(skip[prices.length - 1], max);
+        max = Math.max(sell[prices.length - 1], max);
+        return Math.max(max, 0);
+    }
+}

src/DP/其他问题如股票/需要冷却期的股票交易.java

@@ -0,0 +1,21 @@
+package DP.其他问题如股票;
+
+/**
+ * Created by 周杰伦 on 2018/4/9.
+ */
+public class 需要冷却期的股票交易_双数组 {
+    public int maxProfit(int[] prices) {
+        if(prices == null || prices.length < 2){
+            return 0;
+        }
+        int len = prices.length;
+        int[] sell = new int[len]; //sell[i] means must sell at day i
+        int[] cooldown = new int[len]; //cooldown[i] means day i is cooldown day
+        sell[1] = prices[1] - prices[0];
+        for(int i = 2; i < prices.length; ++i){
+            cooldown[i] = Math.max(sell[i - 1], cooldown[i - 1]);
+            sell[i] = prices[i] - prices[i - 1] + Math.max(sell[i - 1], cooldown[i - 2]);
+        }
+        return Math.max(sell[len - 1], cooldown[len - 1]);
+    }
+}

src/DP/其他问题如股票/需要冷却期的股票交易_双数组.java

@@ -0,0 +1,22 @@
+package DP.字符串编辑;
+
+/**
+ * Created by 周杰伦 on 2018/4/10.
+ */
+public class 字符串复制粘贴 {
+    public int minSteps(int n) {
+        int[] dp = new int[n+1];
+
+        for (int i = 2; i <= n; i++) {
+            dp[i] = i;
+            for (int j = i-1; j > 1; j--) {
+                if (i % j == 0) {
+                    dp[i] = dp[j] + (i/j);
+                    break;
+                }
+
+            }
+        }
+        return dp[n];
+    }
+}

src/DP/字符串编辑/字符串复制粘贴.java

@@ -3,7 +3,7 @@
 /**
  * Created by 周杰伦 on 2018/4/4.
  */
-public class 最长摆动子序列 {
+public class 最长摆动子序列_双数组 {
     public static void main(String[] args) {
         int []a = {1,7,4,9,2,5};
         int []b = {1,17,5,10,13,15,10,5,16,8};