DP-1

problem1.java

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+// Time Complexity : O(m*n)
+// Space Complexity : O(m*n)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+
+
+class Solution {
+    public int coinChange(int[] coins, int amount) {
+        int m = coins.length;
+        int n = amount;
+        int[][] dp = new int[m+1][n+1];
+        dp[0][0] = 0;
+        for(int i=1;i<=n;i++){
+            dp[0][i] = 999999;
+        }
+        for(int i=1;i<=m;i++){
+            for(int j=0;j<=n;j++){
+                if(j<coins[i-1]){
+                    dp[i][j] = dp[i-1][j];
+                }
+                else{
+                    dp[i][j] = Math.min(dp[i-1][j], 1 + dp[i][j - coins[i-1]]);
+                }
+            }
+        }
+        if(dp[m][n]==999999) return -1;
+        return dp[m][n];
+    }
+}

problem2.java

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+// Time Complexity : O(n)
+// Space Complexity : O(1)
+// Did this code successfully run on Leetcode : Yes
+// Any problem you faced while coding this : No
+
+
+class Solution {
+    public int rob(int[] nums) {
+        if(nums.length < 2) return nums[0];
+        int len = nums.length;
+        int prev = nums[0];
+        int current = Math.max(nums[0],nums[1]);
+        for(int i = 2;i<len;i++){
+            int temp = current;
+            current = Math.max(current,nums[i] + prev);
+            prev = temp;
+        }
+        return current;
+    }
+}