Merge pull request #2 from thepushkarp/MayWeek2

Add May Week 2

Author: thepushkarp

MayChallenge/Week2/10:FindtheTownJudge.cpp

@@ -0,0 +1,23 @@
+class Solution {
+public:
+ int findJudge(int N, vector<vector<int>>& trust) {
+ int sum = N*(N+1)/2;
+ int trusts[N + 1], trustedBy[N + 1];
+ for (int i = 1; i < N + 1; i++) {
+ trusts[i] = 0;
+ trustedBy[i] = 0;
+ }
+ for (int i = 0; i < trust.size(); i++) {
+ trusts[trust[i][0]] += trust[i][1];
+ trustedBy[trust[i][1]] += trust[i][0];
+ }
+ for (int i = 1; i < N + 1; i++) {
+ if (trusts[i] == 0) {
+ if (sum - trustedBy[i] == i) {
+ return i;
+ }
+ }
+ }
+ return -1;
+ }
+};

MayChallenge/Week2/11:FloodFill.cpp

@@ -0,0 +1,39 @@
+class Solution {
+public:
+ vector<vector<int>> floodFill(vector<vector<int>>& image, int sr, int sc, int newColour) {
+ int rowSize = image.size();
+ int colSize = image[0].size();
+ int prevColour = image[sr][sc];
+ vector<vector<int>> visited(rowSize, vector<int>(colSize, 0));
+ queue<pair<int, int>> pixelToColour;
+ pixelToColour.push(make_pair(sr, sc));
+ while(pixelToColour.size() > 0) {
+ int r = pixelToColour.front().first;
+ int c = pixelToColour.front().second;
+ image[r][c] = newColour;
+ visited[r][c] = 1;
+ if (r > 0) {
+ if (image[r-1][c] == prevColour and !visited[r-1][c]) {
+ pixelToColour.push(make_pair(r-1, c));
+ }
+ }
+ if (r < rowSize - 1) {
+ if (image[r+1][c] == prevColour and !visited[r+1][c]) {
+ pixelToColour.push(make_pair(r+1, c));
+ }
+ }
+ if (c > 0) {
+ if (image[r][c-1] == prevColour and !visited[r][c-1]) {
+ pixelToColour.push(make_pair(r, c-1));
+ }
+ }
+ if (c < colSize - 1) {
+ if (image[r][c+1] == prevColour and !visited[r][c+1]) {
+ pixelToColour.push(make_pair(r, c+1));
+ }
+ }
+ pixelToColour.pop();
+ }
+ return image;
+ }
+};

MayChallenge/Week2/12:SingleElementinaSortedArray.cpp

@@ -0,0 +1,10 @@
+class Solution {
+public:
+ int singleNonDuplicate(vector<int>& nums) {
+ int ans = 0;
+ for (auto i : nums) {
+ ans^=i;
+ }
+ return ans;
+ }
+};

MayChallenge/Week2/13:RemoveKDigits.cpp

@@ -0,0 +1,32 @@
+class Solution {
+public:
+ string stripLeadingZeros(string str) {
+ int i = 0;
+ for (; i < str.size() - 1; i++) {
+ if (str[i] != '0') break;
+ }
+ str.erase(str.begin(), str.begin() + i);
+ return str;
+ }
+
+ string removeKdigits(string num, int k) {
+ if (k == num.size()) return "0";
+
+ int digitsToKeep = num.size() - k;
+
+ string ans = "";
+ int lastIndex = -1;
+ while (digitsToKeep) {
+ int mini = 10;
+ for (int i = lastIndex + 1; i <= num.size() - digitsToKeep; i++) {
+ if (num[i] - '0' < mini) {
+ mini = num[i] - '0';
+ lastIndex = i;
+ }
+ }
+ ans+=('0' + mini);
+ digitsToKeep--;
+ }
+ return stripLeadingZeros(ans);
+ }
+};

MayChallenge/Week2/14:ImplementTrie.cpp

@@ -0,0 +1,63 @@
+class Trie {
+public:
+ /** Initialize your data structure here. */
+ static const int ALPHA_SIZE = 26;
+ Trie* character[ALPHA_SIZE];
+ bool endOfWord;
+ Trie() {
+ this -> endOfWord = false;
+ for (int i = 0; i < ALPHA_SIZE; i++) {
+ this -> character[i] = nullptr;
+ }
+ }
+
+ /** Inserts a word into the trie. */
+ void insert(string word) {
+ Trie* curr = this;
+ for (int i = 0; i < word.size(); i++) {
+ if (curr -> character[word[i] - 'a'] == nullptr) {
+ curr -> character[word[i] - 'a'] = new Trie();
+ }
+ curr = curr -> character[word[i] - 'a'];
+ }
+ curr -> endOfWord = true;
+ }
+
+ /** Returns if the word is in the trie. */
+ bool search(string word) {
+ if (this == nullptr) {
+ return false;
+ }
+ Trie* curr = this;
+ for (int i = 0; i < word.size(); i++) {
+ curr = curr -> character[word[i] - 'a'];
+ if (curr == nullptr) {
+ return false;
+ }
+ }
+ return curr -> endOfWord;
+ }
+
+ /** Returns if there is any word in the trie that starts with the given prefix. */
+ bool startsWith(string prefix) {
+ if (this == nullptr) {
+ return false;
+ }
+ Trie* curr = this;
+ for (int i = 0; i < prefix.size(); i++) {
+ curr = curr -> character[prefix[i] - 'a'];
+ if (curr == nullptr) {
+ return false;
+ }
+ }
+ return true;
+ }
+};
+
+/**
+ * Your Trie object will be instantiated and called as such:
+ * Trie* obj = new Trie();
+ * obj->insert(word);
+ * bool param_2 = obj->search(word);
+ * bool param_3 = obj->startsWith(prefix);
+ */

MayChallenge/Week2/8:CheckIfItIsaStraightLine.cpp

@@ -0,0 +1,18 @@
+class Solution {
+public:
+ float epsilon = 0.005f;
+ bool checkStraightLine(vector<vector<int>>& coordinates) {
+ if (coordinates.size() == 2) {
+ return true;
+ }
+ bool colinear = true;
+ int x1 = coordinates[0][0], y1 = coordinates[0][1];
+ int x2 = coordinates[1][0], y2 = coordinates[1][1];
+ for (int i = 2; i < coordinates.size(); i++) {
+ int x = coordinates[i][0], y = coordinates[i][1];
+ if ((x - x1)*(y - y2) != (x - x2)*(y - y1))
+ colinear = false;
+ }
+ return colinear;
+ }
+};

MayChallenge/Week2/9:ValidPerfectSquare.cpp

@@ -0,0 +1,10 @@
+class Solution {
+public:
+ bool isPerfectSquare(int num) {
+ long i = 1;
+ while(i*i < num) {
+ i++;
+ }
+ return i*i == num;
+ }
+};