Add 973, 974, 976

Author: moranzcw

Algorithms/973.K-Closest-Points-to-Origin/solution.cpp

@@ -0,0 +1,12 @@
+
+bool cmp(const vector<int> &p1, const vector<int> &p2){
+    return (p1[0]*p1[0] + p1[1]*p1[1]) < (p2[0]*p2[0] + p2[1]*p2[1]);
+}
+
+class Solution {
+public:
+    vector<vector<int>> kClosest(vector<vector<int>>& points, int K) {
+        sort(points.begin(), points.end(), cmp);
+        return vector(points.begin(), points.begin()+K);
+    }
+};

Algorithms/974.Subarray-Sums-Divisible-by-K/solution.cpp

@@ -0,0 +1,21 @@
+class Solution {
+public:
+    int subarraysDivByK(vector<int>& A, int K) {
+        int sum = 0;
+        int length = A.size();
+        vector<int> mod(K,0);
+        for(int i = 0; i < length; i++) {
+        	sum += A[i];
+        	mod[((sum % K) + K) % K]++; // as the sum can be negative, taking modulo twice
+        }
+        
+        sum = 0;
+        for(int i = 0; i < K; i++) {
+        	if(mod[i] > 1) {
+        		sum += (mod[i] - 1) * mod[i] / 2;
+        	}
+        }
+        sum += mod[0];
+        return sum;
+    }
+};

Algorithms/976.Largest-Perimeter-Triangle/solution.cpp

@@ -0,0 +1,21 @@
+bool cmp(int a, int b){
+    return a > b;
+}
+class Solution {
+public:
+    int largestPerimeter(vector<int>& A) {
+        sort(A.begin(), A.end(), cmp);
+        for(int i=0;i<A.size();i++){
+            for(int j=i+1;j<A.size();j++){
+                if(A[j] < A[i]/2)
+                    break;
+                for(int k=j+1;k<A.size();k++){
+                    if(A[k] + A[j] > A[i])
+                        return A[i] + A[j] + A[k];
+                    break;
+                }
+            }
+        }
+        return 0;
+    }
+};

README.md

@@ -663,4 +663,10 @@
 
 [958.Check-Completeness-of-a-Binary-Tree](Algorithms/958.Check-Completeness-of-a-Binary-Tree/solution.cpp)
 
-[959.Regions-Cut-By-Slashes](Algorithms/959.Regions-Cut-By-Slashes/solution.cpp)
+[959.Regions-Cut-By-Slashes](Algorithms/959.Regions-Cut-By-Slashes/solution.cpp)
+
+[973.K-Closest-Points-to-Origin](Algorithms/973.K-Closest-Points-to-Origin/solution.cpp)
+
+[974.Subarray-Sums-Divisible-by-K](Algorithms/974.Subarray-Sums-Divisible-by-K/solution.cpp)
+
+[976.Largest-Perimeter-Triangle](Algorithms/976.Largest-Perimeter-Triangle/solution.cpp)