完成leecode第7题。

Author: ssjssh

.gitignore

@@ -58,4 +58,8 @@ docs/_build/
 # PyBuilder
 target/
 
-test.py
+test.py
+
+#c out file
+*.out
+*.exe

src/ssj/leecode/reverse_integer.c

@@ -0,0 +1,71 @@
+/**
+*本题目使用C编写，因为Python的int类型是无限大的，要判断一个数字是否溢出非常简单，祝需要和2^32-1比较就好了
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+
+
+int intToString(int i,char *arr){
+    int t_len = sprintf(arr,"%d",i);
+    arr[t_len] = '\0';
+    return t_len;
+}
+int willOverflow(char *result,int is_negative){
+    char min_str[40];
+    char max_str[40];
+    int max_len = intToString(INT_MAX,max_str);
+    int min_len = intToString(INT_MIN,min_str);
+    int result_len = strlen(result);
+    if((is_negative&&result_len<min_len) || (!is_negative&&result_len<max_len)){
+       return 0;
+    }
+    return is_negative?(strcmp(min_str,result)<0):(strcmp(max_str,result)<0);
+}
+int reverse(int x) {
+    char *s_char,*tar_c;
+    int result=0;
+    char intStr[40];
+    int is_negative=0;
+    tar_c = intStr;
+    if(x<0){
+        *tar_c = '-';
+        tar_c++;
+        x = -x;
+        is_negative=1;
+    }
+
+    while(x > 0){
+        *tar_c = x%10+'0';
+        x /= 10;
+        tar_c++;
+    }
+    *tar_c='\0';
+    if(willOverflow(intStr,is_negative)){
+           return 0;
+    }
+    for(tar_c = intStr;(*tar_c)!='\0';tar_c++){
+        if ((*tar_c)!='-'){
+
+            result *= 10;
+            result += (*tar_c)-'0';
+        }
+    }
+    if(intStr[0]=='-'){
+        result = -result;
+    }
+
+    return result;
+}
+
+
+
+int main(){
+    printf("%d\n",reverse(1231312));
+    printf("%d\n",reverse(123));
+    printf("%d\n",reverse(-1231312));
+    printf("%d\n",reverse(1000000003));
+    printf("%d\n",reverse(-1000000003));
+    return 0;
+}