完成leecode第8题。

Author: ssjssh

src/ssj/leecode/atoi.c

@@ -0,0 +1,98 @@
+#include <stdio.h>
+#include <string.h>
+#include <limits.h>
+
+
+static int intToString(int i,char *arr){
+    int t_len = sprintf(arr,"%d",i);
+    arr[t_len] = '\0';
+    return t_len;
+}
+static int myStrcmp(char *start,char *end,char *other){
+    for(char *c1 = start,*c2 = other;c1<=end&&c2!='\0';c1++,c2++){
+        if (*c1 > *c2){
+            return 1;
+        }else if(*c1 < *c2){
+            return -1;
+        }
+    }
+    return 0;
+}
+
+int myAtoi(char* str) {
+    int is_negative = 0;
+    char *start=NULL,*end=NULL;
+    for(char *c=str;c!='\0';c++){
+        if(start==NULL && (*c == ' ' || *c =='\n' || *c == '\t')){
+            continue;
+        }else if((*c=='-' || (*c >='0' && *c<='9') || *c=='+') && start==NULL){
+            start = c;
+            if(*c == '-'){
+                is_negative=1;
+            }
+        }else if(*c >='0' && *c<='9'&& start!=NULL){
+             end = c;
+        }else{
+            break;
+        }
+    }
+
+    if(start==NULL){
+        return 0;
+    }else if (end==NULL){
+        end = start;
+    }
+
+    if(*start == '+'){
+        start++;
+    }
+
+//    printf("%c:%c\n",*start,*end);
+    //检查是否越界
+    int result_len = end - start + 1;
+    if(is_negative){
+        char min_str[40];
+        int min_len = intToString(INT_MIN,min_str);
+        if(result_len>min_len || (result_len == min_len && myStrcmp(start,end,min_str)>0)){
+            return INT_MIN;
+        }
+    }else{
+        char max_str[40];
+        int max_len = intToString(INT_MAX,max_str);
+        if(result_len>max_len || (result_len == max_len && myStrcmp(start,end,max_str)>0)){
+             return INT_MAX;
+        }
+    }
+
+    int result = 0;
+
+//       printf("%c:%c",*start,*end);
+    for(char *c=start;c<=end;c++){
+        if(*c != '-' && *c != '+'){
+            result *= 10;
+            result += (*c - '0');
+        }
+    }
+
+    if(*start=='-'){
+        result = -result;
+    }
+    return result;
+}
+
+
+int main(){
+    printf("%d\n",myAtoi("+1231312"));
+    printf("%d\n",myAtoi("      -11919730356x"));
+    printf("%d\n",myAtoi("    +1146905820n1"));
+    printf("%d\n",myAtoi("1"));
+    printf("%d\n",myAtoi("123"));
+    printf("%d\n",myAtoi("-1231312"));
+    printf("%d\n",myAtoi("-1231312fqwef"));
+    printf("%d\n",myAtoi("-1231312 992"));
+    printf("%d\n",myAtoi("3000000001"));
+    printf("%d\n",myAtoi("-3000000001"));
+    printf("%d\n",myAtoi("wefwqef-3000000001"));
+    printf("%d\n",myAtoi("   -3000000001"));
+    return 0;
+}