diff --git a/setmismatch.c b/setmismatch.c
new file mode 100644
index 0000000..e25b4dd
--- /dev/null
+++ b/setmismatch.c
@@ -0,0 +1,64 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int* findErrorNums(int* nums, int numsSize, int* returnSize) {
+    int xr = 0; // Initialize a variable to store the XOR result.
+
+    for (int i = 0; i < numsSize; i++) {
+        xr ^= nums[i]; // XOR all elements in the nums array.
+        xr ^= (i + 1); // XOR with expected values (1 to n).
+    }
+
+    int idx = 0;
+
+    // Find the rightmost set bit (indicated by 'idx') in the XOR result.
+    while (1) {
+        if (xr & (1 << idx)) break;
+        idx++;
+    }
+
+    // Initialize variables for the first and second numbers to be found.
+    int f = 0;
+
+    for (int i = 0; i < numsSize; i++) {
+        if (nums[i] & (1 << idx)) f ^= nums[i]; // XOR elements with the same set bit as idx.
+        int x = i + 1;
+        if (x & (1 << idx)) f ^= x; // XOR expected values with the same set bit as idx.
+    }
+
+    int s = xr ^ f; // Calculate the second number.
+
+    // Check if 'f' already exists in the nums array.
+    int flag = 0;
+    for (int i = 0; i < numsSize; i++) {
+        if (nums[i] == f) {
+            flag = 1;
+            break;
+        }
+    }
+
+    *returnSize = 2;
+
+    int* result = (int*)malloc(2 * sizeof(int));
+    if (flag) {
+        result[0] = f;
+        result[1] = s;
+    } else {
+        result[0] = s;
+        result[1] = f;
+    }
+
+    return result;
+}
+
+int main() {
+    int nums[] = {1, 2, 2, 4};
+    int numsSize = sizeof(nums) / sizeof(nums[0]);
+    int returnSize;
+    int* result = findErrorNums(nums, numsSize, &returnSize);
+
+    printf("Result: [%d, %d]\n", result[0], result[1]);
+    free(result);
+
+    return 0;
+}