Create 188. Best Time to Buy and Sell Stock IV

Author: khushi3004

188. Best Time to Buy and Sell Stock IV

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+class Solution {
+    public int maxProfit(int k, int[] prices) {
+        
+        int n = prices.length;
+        int[][] dp = new int[k+1][n];
+        
+        if(n < 2) return 0;
+        
+        for(int i = 1; i <= k; i++) {
+            for(int j = 1; j < n; j++) {
+                dp[i][j] = Math.max(dp[i][j-1], helper(i, j, prices, dp));
+            }
+        }
+        
+        return dp[k][n-1];
+        
+    }
+    
+    private int helper(int k, int x, int[] prices, int[][] dp){
+        int max = 0;
+        for(int i = 0; i < x; i++) {
+            //Sell on day_x, buy on day_i and add profit from (i-1) transsactions dp[k-1][i]
+            max = Math.max(max, prices[x]-prices[i] + dp[k-1][i]);
+        }
+        return max;
+    }
+}
+
+
+
+class Solution {
+    public int maxProfit(int k, int[] prices) {
+        
+        int n = prices.length;
+        int[][] dp = new int[k+1][n];   //Space : O(KN)
+        
+        if(n < 2) return 0;
+        
+        //Time O(K*N)
+        for(int i = 1; i <= k; i++) {
+            int effectiveBuyPrice = prices[0];
+            for(int j = 1; j < n; j++) {
+                //Profit by selling on current price (j) 
+                // Profit = SP-EBP
+                // SP => price[j]
+                // BP => Effective Buy Price -> price[j] - previous profit (dp[k-1][j])
+                dp[i][j] = Math.max(dp[i][j-1], prices[j] - effectiveBuyPrice);
+                effectiveBuyPrice = Math.min(effectiveBuyPrice, prices[j] - dp[i-1][j]);
+            }
+        }
+        return dp[k][n-1];   
+    }
+}