🚀 10-Aug-2020

Author: sureshmangs

.gitignore

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-temporary/
+temporary/
+Notes.md

competitive programming/leetcode/1037. Valid Boomerang.cpp

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+A boomerang is a set of 3 points that are all distinct and not in a straight line.
+
+Given a list of three points in the plane, return whether these points are a boomerang.
+
+
+
+Example 1:
+
+Input: [[1,1],[2,3],[3,2]]
+Output: true
+Example 2:
+
+Input: [[1,1],[2,2],[3,3]]
+Output: false
+
+
+Note:
+
+points.length == 3
+points[i].length == 2
+0 <= points[i][j] <= 100
+
+
+
+
+
+
+
+
+// Using Herons Formula
+// If area of triangle is zero, => collinear
+
+class Solution {
+public:
+    bool isBoomerang(vector<vector<int>>& points) {
+        int x1=points[0][0];
+        int y1=points[0][1];
+        int x2=points[1][0];
+        int y2=points[1][1];
+        int x3=points[2][0];
+        int y3=points[2][1];
+
+        double a = sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
+        double b = sqrt((x3-x2)*(x3-x2)+(y3-y2)*(y3-y2));
+        double c = sqrt((x1-x3)*(x1-x3)+(y3-y1)*(y3-y1));
+
+        double s = (a+b+c)/2;
+
+        double area = sqrt(s*(s-a)*(s-b)*(s-c));
+
+        return area ? true: false;
+
+    }
+};

competitive programming/leetcode/12. Integer to Roman.cpp

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+Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
+
+Symbol       Value
+I             1
+V             5
+X             10
+L             50
+C             100
+D             500
+M             1000
+For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.
+
+Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:
+
+I can be placed before V (5) and X (10) to make 4 and 9.
+X can be placed before L (50) and C (100) to make 40 and 90.
+C can be placed before D (500) and M (1000) to make 400 and 900.
+Given an integer, convert it to a roman numeral. Input is guaranteed to be within the range from 1 to 3999.
+
+Example 1:
+
+Input: 3
+Output: "III"
+Example 2:
+
+Input: 4
+Output: "IV"
+Example 3:
+
+Input: 9
+Output: "IX"
+Example 4:
+
+Input: 58
+Output: "LVIII"
+Explanation: L = 50, V = 5, III = 3.
+Example 5:
+
+Input: 1994
+Output: "MCMXCIV"
+Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
+
+
+
+
+
+
+
+
+
+
+class Solution {
+public:
+    string intToRoman(int num) {
+        vector<string> roman={"M","CM","D","CD","C","XC","L","XL","X","IX","V", "IV","I"};
+        vector<int> no= {1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1};
+        string res;
+        int i=0;
+        while(num!=0){
+            while(num>=no[i]){
+                num-=no[i];
+                res+=roman[i];
+            }
+            i++;
+        }
+        return res;
+    }
+};

competitive programming/leetcode/13. Roman to Integer.cpp

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+Roman numerals are represented by seven different symbols: I, V, X, L, C, D and M.
+
+Symbol       Value
+I             1
+V             5
+X             10
+L             50
+C             100
+D             500
+M             1000
+For example, two is written as II in Roman numeral, just two one's added together. Twelve is written as, XII, which is simply X + II. The number twenty seven is written as XXVII, which is XX + V + II.
+
+Roman numerals are usually written largest to smallest from left to right. However, the numeral for four is not IIII. Instead, the number four is written as IV. Because the one is before the five we subtract it making four. The same principle applies to the number nine, which is written as IX. There are six instances where subtraction is used:
+
+I can be placed before V (5) and X (10) to make 4 and 9.
+X can be placed before L (50) and C (100) to make 40 and 90.
+C can be placed before D (500) and M (1000) to make 400 and 900.
+Given a roman numeral, convert it to an integer. Input is guaranteed to be within the range from 1 to 3999.
+
+Example 1:
+
+Input: "III"
+Output: 3
+Example 2:
+
+Input: "IV"
+Output: 4
+Example 3:
+
+Input: "IX"
+Output: 9
+Example 4:
+
+Input: "LVIII"
+Output: 58
+Explanation: L = 50, V= 5, III = 3.
+Example 5:
+
+Input: "MCMXCIV"
+Output: 1994
+Explanation: M = 1000, CM = 900, XC = 90 and IV = 4.
+
+
+
+
+
+
+
+
+
+
+
+
+
+class Solution {
+public:
+    int romanToInt(string s) {
+        int res=0;
+        int n=s.length();
+        unordered_map<char, int> mp;
+        mp.insert({'I', 1});
+        mp.insert({'V', 5});
+        mp.insert({'X', 10});
+        mp.insert({'L', 50});
+        mp.insert({'C', 100});
+        mp.insert({'D', 500});
+        mp.insert({'M', 1000});
+
+        for(int i=0;i<n-1;i++){
+            if(mp[s[i]]>=mp[s[i+1]]) res+=mp[s[i]];
+            else res+=-mp[s[i]];
+        }
+        res+=mp[s[n-1]];
+
+        return res;
+    }
+};

competitive programming/leetcode/2020-August-Challenge/Day-10-Excel Sheet Column Number.cpp

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+Given a column title as appear in an Excel sheet, return its corresponding column number.
+
+For example:
+
+    A -> 1
+    B -> 2
+    C -> 3
+    ...
+    Z -> 26
+    AA -> 27
+    AB -> 28
+    ...
+Example 1:
+
+Input: "A"
+Output: 1
+Example 2:
+
+Input: "AB"
+Output: 28
+Example 3:
+
+Input: "ZY"
+Output: 701
+
+
+Constraints:
+
+1 <= s.length <= 7
+s consists only of uppercase English letters.
+s is between "A" and "FXSHRXW".
+
+
+
+
+
+
+
+
+
+
+class Solution {
+public:
+    int titleToNumber(string s) {
+        int res=0, k=0;
+        int n=s.length();
+        for(int i=n-1;i>=0;i--){
+            int ch=(s[i]-'A')+1;
+            res+=ch*pow(26,k++);
+        }
+        return res;
+    }
+};

competitive programming/leetcode/204. Count Primes.cpp

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+Count the number of prime numbers less than a non-negative number, n.
+
+Example:
+
+Input: 10
+Output: 4
+Explanation: There are 4 prime numbers less than 10, they are 2, 3, 5, 7.
+
+
+
+
+
+
+
+
+
+
+
+
+class Solution {
+public:
+    int countPrimes(int n) {
+        bool seive[n+1];
+        fill(seive, seive+n+1, true);
+        for(int p=2; p*p<=n;p++){
+            if(seive[p]==true){
+                for(int i=p*p;i<=n;i+=p){
+                    seive[i]=false;
+                }
+            }
+        }
+
+        int cnt=0;
+        for(int p=2;p<n;p++){ // prime less than n, not including n
+            if(seive[p]==true) cnt++;
+
+        }
+        return cnt;
+    }
+};

competitive programming/leetcode/326. Power of Three.cpp

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+Given an integer, write a function to determine if it is a power of three.
+
+Example 1:
+
+Input: 27
+Output: true
+Example 2:
+
+Input: 0
+Output: false
+Example 3:
+
+Input: 9
+Output: true
+Example 4:
+
+Input: 45
+Output: false
+Follow up:
+Could you do it without using any loop / recursion?
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+class Solution {
+public:
+    bool isPowerOfThree(int n) {
+        if(n<=0) return false;
+        double res = log10(n)/log10(3);
+        return res==int(res);
+    }
+};