solve 7

1 files changed, 52 insertions, 0 deletions

diff --git a/0007/main.c b/0007/main.c
new file mode 100644
index 0000000..a110e30
--- /dev/null
+++ b/0007/main.c
@@ -0,0 +1,52 @@
+#include <stdint.h>
+#include <limits.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdbool.h>
+
+int reverse(int x){
+    if (x == INT_MIN) {
+        return 0;
+    }
+    char buf[10];
+    memset(buf, 0, 10);
+    int i = 0;
+    bool pos = x > 0 ? true : false;
+    uint32_t ux = x > 0 ? x : -x;
+    while (ux > 0) {
+        buf[i] = ux % 10;
+        ux = ux / 10;
+        i++;
+    }
+    uint32_t r = 0;
+    int len = i;
+    for (int i = 0; i < len && i < 9; i++) {
+        r = r * 10 + buf[i];
+    }
+    if (len <= 9) {
+        return pos ? r : -r;
+    }
+    if (r < 214748364) {
+        r = r * 10 + buf[9];
+        return pos ? r : -r;
+    }
+    if (r > 214748364) {
+        return 0;
+    }
+    if (pos) {
+        if (buf[9] > 7) {
+            return 0;
+        }
+    } else {
+        if (buf[9] > 8) {
+            return 0;
+        }
+    }
+    r = r * 10 + buf[9];
+    return pos ? r : -r;
+}
+
+int main() {
+    printf("%d\n", reverse(123));
+    printf("%d\n", reverse(-123));
+}
\ No newline at end of file