"Single Number III"

Author: lennylxx

README.md

@@ -44,7 +44,7 @@ The `☢` means that you need to have a LeetCode Premium Subscription.
 | 264 | [Ugly Number II]                                             |                    |
 | 263 | [Ugly Number]                                                | [C](src/263.c)     |
 | 261 | [Graph Valid Tree] ☢                                         |                    |
-| 260 | [Single Number III]                                          |                    |
+| 260 | [Single Number III]                                          | [C](src/260.c)     |
 | 259 | [3Sum Smaller] ☢                                             |                    |
 | 258 | [Add Digits]                                                 | [C](src/258.c)     |
 | 257 | [Binary Tree Paths]                                          | [C++](src/257.cpp) |

src/260.c

@@ -0,0 +1,55 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+/**
+ * Return an array of size *returnSize.
+ * Note: The returned array must be malloced, assume caller calls free().
+ */
+int* singleNumber(int* nums, int numsSize, int* returnSize) {
+    if (nums == NULL || returnSize == NULL) return 0;
+    *returnSize = 2;
+    int *ans = (int *)calloc(*returnSize, sizeof(int));
+
+    int x = 0;
+    int i;
+    for (i = 0; i < numsSize; i++) {
+        x ^= nums[i];
+    }
+
+    /* get first 1 in xor */
+    int k = 0;
+    while (((x >> k) & 1) == 0) k++;
+
+    /* group numbers in two by k-bit */
+    int a = 0, b = 0;
+    for (i = 0; i < numsSize; i++) {
+        if (nums[i] & (1 << k)) {
+            a ^= nums[i];
+        }
+        else {
+            b ^= nums[i];
+        }
+    }
+
+    ans[0] = a;
+    ans[1] = b;
+
+    return ans;
+}
+
+int main () {
+    int nums[] = {1, 2, 1, 3, 2, 5};
+    int returnSize = 0;
+
+    int *ans = singleNumber(nums, sizeof(nums) / sizeof(nums[0]), &returnSize);
+
+    int i;
+    for (i = 0; i < returnSize; i++) {
+        printf("%d ", ans[i]);
+    }
+    printf("\n");
+
+    free(ans);
+
+    return 0;
+}