week 01, home works

Author: rong-kai

Week_01/id_13/groupAnagrams.js

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+/**
+ * @param {string[]} strs
+ * @return {string[][]}
+ */
+var groupAnagrams = function(strs) { 
+    let res = {};
+    for (let str of strs) {
+        let tmp = str.split('').sort().join('');
+        (res[tmp] == null) ? res[tmp] = [str] : res[tmp].push(str); 
+    }
+    return Object.values(res);
+};
+
+let input= ["eat", "tea", "tan", "ate", "nat", "bat"];
+console.log(groupAnagrams(input));

Week_01/id_13/myPow.js

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+/**
+ * @param {number} x
+ * @param {number} n
+ * @return {number}
+ */ 
+ 
+var myPow = function(x, n) {
+    if(n == 1) return x;
+    if(n == 0) return 1;
+    if(n < 0) return 1/myPow(x,-n);
+    if(n%2==0)
+    {
+        let val= myPow(x,n/2);
+        return val*val;
+    }
+    else
+    {
+        let val = myPow(x,(n-1)/2);
+        return val*val*x;
+    }
+    
+}
+console.log(myPow(0.00001,2147483647));

Week_01/id_13/removeDuplicates.js

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+/**
+ * @param {number[]} nums
+ * @return {number}
+ */
+var removeDuplicates = function(nums) {
+    if(nums.length==0) return nums;
+    let start = 0; 
+    for (let index = 0; index < nums.length; index++) {  
+         if(nums[start]!=nums[index])
+         {
+             start++;
+             nums[start] = nums[index]; 
+         } 
+    }  
+     
+     //return nums ;
+    return start;
+    
+};
+
+let nums=[1,1,2];
+console.log(removeDuplicates(nums));
+

Week_01/id_13/rotate.js

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+var rotate = function(nums, k) {
+    if(nums.length<2) return nums;
+    if(k>0)
+    {
+        k=k%nums.length;
+        reverse(nums,0,nums.length-1);
+        reverse(nums,0,k-1);
+        reverse(nums,k,nums.length-1);
+    }
+    return nums;
+
+}; 
+
+function reverse(nums,start,end)
+{
+    if(!nums || !nums.length || start >=end) return  ;
+    while (start<end) {
+        let temp = nums[start];
+        nums[start] = nums[end];
+        nums[end] = temp;
+        start++;
+        end --;
+    }
+    return nums;
+
+}
+let nums=[1,2,3,4,5,6,7];
+let k = 3;
+console.log(rotate(nums,k));

Week_01/id_13/swapPairs.js

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+var swapPairs = function(head) {
+    if(!head || !head.next) return head;
+    let dummy = new ListNode(0);
+    dummy.next = head;
+    let current = dummy;
+    while (current.next && current.next.next)
+    {
+        let n = current.next;
+        let nn =  current.next.next;
+        current.next.next =  current.next.next.next;
+        current.next = nn;
+        current.next.next=n;
+        current = current.next.next
+            
+    }
+    return dummy.next; 
+};

Week_01/id_13/threeSum.js

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+/**
+ * @param {number[]} nums
+ * @return {number[][]}
+ */
+ 
+var threeSum = function(nums) { 
+    if(nums.length < 3) return [];
+    nums.sort(function(a,b){return a-b;});  
+    let start= 0; 
+    let result = new Map(); 
+    while(nums.length-1>start+1)
+    {
+        let end = nums.length-1;
+        let index = start+1;
+        while(index<end)
+        { 
+            
+            let sum = nums[start]+nums[index] + nums[end];
+            if(sum == 0 )
+            {
+                let newArray = [nums[start],nums[index],nums[end]];
+                result.set(newArray.join(''),newArray); 
+                while(nums[index]==nums[index+1])
+                {
+                    index++;
+                }
+                index++;
+                continue;
+            }
+            if(sum >0)
+            {
+                while(nums[end]==nums[end-1])
+                    {
+                        end --;
+                    }
+                end = end-1; 
+            }
+            else
+            {
+                while(nums[index]==nums[index+1])
+                {
+                    index++;
+                }
+                index++;
+            }
+        }  
+       start = start+1; 
+    }
+    let resultArray = new Array(); 
+    result.forEach(element => {
+       resultArray.push(element);
+        
+    });
+    
+    return resultArray;
+    
+};
+
+let  nums = [-4,-2,-2,-2,0,1,2,2,2,3,3,4,4,6,6];
+console.log(threeSum(nums));

Week_01/id_13/trap.js

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+/**
+ * @param {number[]} height
+ * @return {number}
+ */
+var trap = function(height) {
+    if (height.length<2) return 0; 
+    let head = 0;
+    let tail = head+1;
+    let totalArea=0;
+    let temp=0;
+    while(tail<height.length)
+    {  
+        temp = temp+height[tail-1]; 
+        if(height[tail]>height[head])
+        {  
+            let a= (tail-head) * height[head] - temp; 
+            totalArea +=  a;
+            temp=0; 
+            head= tail; 
+        }
+        tail ++; 
+    }  
+    head = height.length-1;
+    tail = head-1;
+    temp = 0;
+    while(tail >=0 )
+    {
+        temp = temp+height[tail+1];
+        if(height[tail]>=height[head])
+        { 
+            let a= (head-tail)*height[head]-temp;
+            totalArea +=  a;
+            temp=0;
+            head= tail;
+        }
+        tail --;
+    }
+    return totalArea;
+};
+ 
+let height=[2,0,2];
+console.log(trap(height));