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authorjack <[email protected]>2024-06-14 13:13:15 -0600
committerjack <[email protected]>2024-06-14 13:13:15 -0600
commitd343a3b18dbaca9297d4f7b2280c4a16f0a5c8aa (patch)
tree96df922dae2a5073d9a50ea70c7aae6aa37e3ebe /num_good_pair.c
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+// 1512. Number of Good Pairs
+#include <stdio.h>
+#include <stdlib.h>
+
+/*
+ * given an array of integers 'nums', return the number of good pairs. a pair
+ * '(i, j)' is called good if 'nums[i] == nums[j]' and 'i < j'
+ */
+
+int numIdenticalPairs(int *nums, int nums_size) {
+ int max = nums[0];
+ for (int i = 0; i < nums_size; i++)
+ max = nums[i] > max ? nums[i] : max;
+ max++;
+ int *arr = (int *)calloc(max, sizeof(int));
+ for (int i = 0; i < nums_size; i++)
+ arr[nums[i]]++;
+ int ans = 0;
+ for (int i = 0; i < max; i++)
+ if (arr[i] > 1)
+ ans += (arr[i] * (arr[i] - 1) / 2);
+ free(arr);
+ return ans;
+}
+
+int main() {
+ int n1[] = {1, 2, 3, 1, 1, 3}, n2[] = {1, 1, 1, 1}, n3[] = {1, 2, 3};
+ printf("%d\n", numIdenticalPairs(n1, 6)); // expect: 4
+ printf("%d\n", numIdenticalPairs(n2, 4)); // expect: 6
+ printf("%d\n", numIdenticalPairs(n3, 3)); // expect: 0
+}