Merge intervals algorithm

atoi.cpp

@@ -0,0 +1,50 @@
+#include <iostream>
+using namespace std;
+int myAtoi(string str) {
+        int n=str.size();
+        int i=0;
+        while(i<n && str[i]==' '){
+            i++;
+        }
+        if(i==n){
+            return 0;
+        }
+        int sign=1;
+        if(str[i]=='-'){
+            sign=-1;
+            i++;
+        }
+        else if(str[i]=='+'){
+            i++;
+        }
+        if(i==n || !(str[i]>='0' && str[i]<='9')){
+            return 0;
+        }
+        long long ans=0;
+        for(i;i<n;i++){
+            if(str[i]>='0' && str[i]<='9'){
+                if(sign==1){
+                    if(INT_MAX/10<ans){
+                        return INT_MAX;
+                    }
+                    if(INT_MAX/10==ans && str[i]>'7'){
+                        return INT_MAX;
+                    }
+                }
+                if(sign==-1){
+                    if(INT_MAX/10<ans){
+                        return INT_MIN;
+                    }
+                    if(INT_MAX/10==ans && str[i]>'8'){
+                        return INT_MIN;
+                    }
+                }
+                ans*=10;
+                ans+=str[i]-'0';
+            }
+            else{
+                break;
+            }
+        }
+        return sign*ans;
+    }

merge_intervals.cpp

@@ -0,0 +1,22 @@
+#include<iostream>
+using namespace std;
+vector<vector<int>> merge(vector<vector<int>> &intervals)
+{
+  sort(intervals.begin(), intervals.end());
+  vector<vector<int>> ans;
+  int n = intervals.size();
+  int end_idx = -1;
+  for (int i = 0; i < n; i++)
+  {
+    if (intervals[i][0] > end_idx)
+    {
+      ans.push_back(intervals[i]);
+    }
+    else
+    {
+      ans[ans.size() - 1][1] = max(end_idx, intervals[i][1]);
+    }
+    end_idx = max(end_idx, intervals[i][1]);
+  }
+  return ans;
+}

search_in_rotated_array.cpp

@@ -0,0 +1,41 @@
+#include <iostream>
+using namespace std;
+int search(vector<int>& nums, int target) {
+        int n=nums.size();
+        if(n==0){
+            return -1;
+        }
+        int l=0,h=n-1;
+        while(l<h){
+            int mid=(l+h)/2;
+            if(nums[mid]>nums[h]){
+                l=mid+1;
+            }
+            else{
+                h=mid;
+            }
+        }
+        int start=l;
+        cout<<start;
+        if(nums[n-1]>=target){
+            l=start;
+            h=n-1;
+        }
+        else{
+            l=0;
+            h=start-1;
+        }
+        while(l<=h){
+            int mid=(l+h)/2;
+            if(nums[mid]==target){
+                return mid;
+            }
+            if(nums[mid]<target){
+                l=mid+1;
+            }
+            else{
+                h=mid-1;
+            }
+        }
+        return -1;
+    }