add number-of-boomerangs.c

Author: lightmen

c/hash-table/number-of-boomerangs.c

@@ -0,0 +1,91 @@
+struct node {
+    int key;
+    int value;
+    struct node *left;
+    struct node *right;
+};
+
+struct node * node_add(struct node *head, int key)
+{
+    struct node *new_node, *cur;
+    new_node = malloc(sizeof(struct node));
+    new_node->key = key;
+    new_node->value = 1;
+    new_node->left = NULL;
+    new_node->right = NULL;
+    if(head == NULL)
+        return new_node;
+
+    cur = head;
+    while(cur){
+        if(cur->key == key){
+            free(new_node);
+            cur->value++;
+            break;
+        }else if(cur->key > key){
+            if(cur->left == NULL){
+                cur->left = new_node;
+                break;
+            }
+            cur = cur->left;
+        }else{
+            if(cur->right == NULL){
+                cur->right = new_node;
+                break;
+            }
+            cur = cur->right;
+        }
+    }
+
+    return head;
+}
+
+void node_free(struct node *head)
+{
+    if(head == NULL)
+        return ;
+    node_free(head->left);
+    node_free(head->right);
+    free(head);
+}
+
+int get_value_by_key(struct node *head, int key)
+{
+    struct node *cur = head;
+    while(cur){
+        if(cur->key == key)
+            break;
+        if(cur->key > key)
+            cur = cur->left;
+        else
+            cur = cur->right;
+    }
+
+    return cur ? cur->value : 0;
+}
+
+int dist(int x1, int y1, int x2, int y2)
+{
+    return (x2 - x1) * (x2 - x1) + (y2 - y1) * (y2 - y1);
+}
+
+int numberOfBoomerangs(int** points, int pointsRowSize, int pointsColSize) {
+    int i,j;
+    struct node *head;
+    int ret = 0;
+    int key;
+
+    for(i = 0; i < pointsRowSize; ++i){
+        head = NULL;
+        for(j = 0; j < pointsRowSize; ++j){
+            if(i == j)
+                continue;
+            key = dist(points[i][0], points[i][1], points[j][0], points[j][1]);
+            ret += (2 * get_value_by_key(head, key));
+            head = node_add(head, key);
+        }
+        node_free(head);
+    }
+
+    return ret;
+}