Challenge 1 - Two Sum

Find min in rotated sorted array/Solution.java

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+class Solution {
+    public int findMin(int[] nums) {
+     int start = 0;
+     int end =nums.length-1;
+     int mid=0;
+     while(start<=end){
+         mid=start+(end-start)/2;
+
+        if(nums[mid]>=nums[end]){
+            start=mid+1;
+        }
+        else {
+            end=mid;
+        }
+     }  
+
+     return nums[mid]; 
+    }
+}

best-time-to-buy-stock/Solution.java

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+class Solution {
+    public int maxProfit(int[] prices) {
+        int max=0;
+        int minAmount=prices[0];
+
+        for(int i=1;i<prices.length;i++){
+           int profit=prices[i]-minAmount;
+            max=Math.max(max,profit);
+            minAmount=Math.min(minAmount,prices[i]);
+        }
+        return max;
+    }
+}

contains duplicate/Solution.java

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+class Solution {
+    public boolean containsDuplicate(int[] nums) {
+        Set<Integer> hash = new HashSet<>();
+
+        for(int i =0;i<nums.length;i++){
+            if(!hash.add(nums[i])){
+                return true;
+            }
+        }
+
+        return false;
+    }
+}

max product subarray/Solution.java

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+class Solution {
+    public int maxProduct(int[] nums) {
+      int max=nums[0];
+      int min=nums[0];
+      int globalMax=nums[0];
+      for (int i =1;i<nums.length;i++){
+
+        int tmp=max;
+        max=Math.max(nums[i],Math.max(max*nums[i],min*nums[i]));
+        min=Math.min(nums[i],Math.min(tmp*nums[i],min*nums[i]));
+
+        globalMax=Math.max(max,globalMax);
+      }
+
+      return globalMax;  
+    }
+}

max subarray/Solution.java

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+class Solution {
+    public int maxSubArray(int[] nums) {
+      int max=nums[0];
+      int value=nums[0];
+      for(int i=1;i<nums.length;i++){
+        if(value<0){
+            if(nums[i]>=value){
+                value=nums[i];
+                max=Math.max(value,max);
+                continue;
+            }
+        }
+        else{
+            value+=nums[i];
+            max=Math.max(max,value);
+        }
+
+      }
+
+      return max;
+    }
+}

product of array/Solution.java

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+class Solution {
+    public int[] productExceptSelf(int[] nums) {
+        int[] arr=new int[nums.length];
+        int value=1;
+        int[] prod=new int[nums.length];
+        for(int i=0;i<nums.length;i++){
+            value*=nums[i];
+           arr[i]=value;
+        }
+
+        int j =1;
+        int k = arr.length-2;
+
+        for(int i=nums.length-1;i>0;i--){
+
+          prod[i]=arr[k]*j;
+          j=j*nums[i];
+          k--;
+        }
+        prod[0]=j;
+        return prod;
+    }
+}

sum of integers/Solution.java

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+class Solution {
+    public int getSum(int a, int b) {
+        int carry =(a&b)<<1;
+
+        int sum=a^b;
+        int total = sum ^ carry;
+
+        System.out.println(total);
+
+        while(carry!=0){
+            carry=(sum&carry)<<1;
+            sum=total;
+            total^=carry;
+
+        }
+
+        return total;
+    }
+}

twosum/Solution.java

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+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        int[] arr = new int[2];
+        Map<Integer,Integer> hash=new HashMap<>();
+
+        for(int i=0;i<nums.length;i++){
+            if(hash.containsKey(target-nums[i])){
+                arr[0]=hash.get(target-nums[i]);
+                arr[1]=i;
+                return arr;
+            }
+
+            hash.put(nums[i],i);
+        }
+
+        return arr;
+
+    }
+}