Create 1925. Count Square Sum Triples (#953)

Author: Chayandas07

1925. Count Square Sum Triples

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+class Solution {
+public:
+    static int GCD(unsigned x, unsigned y){
+        const int bx=countr_zero(x), by=countr_zero(y);
+        const int bb=min(bx, by);
+        x>>=bx, y>>=by;
+        for(unsigned r; y; y=min(y, r)){
+            r=x%y;
+            x=exchange(y, r);
+        }
+        return x<<bb;
+    }
+    static int countTriples(int n) {
+        int cnt=0;
+        int nsqrt=sqrt(n);
+        for (int s=2; s<=nsqrt; s++) {
+            for (int t=1+(s&1); t<s; t+=2) {
+                if (GCD(s, t)!=1) continue;
+
+            //    int a=s*s-t*t;
+            //    int b=2*s*t;
+                int c=s*s+t*t;
+
+                if (c>n) break;
+
+                // k multiples: ka, kb, kc
+                int kmax=n/c;
+                // count (a,b,c) and (b,a,c)
+                cnt+=2*kmax;
+            }
+        }
+        return cnt;
+    }
+};