編程演算法 - 把字串轉換為整數 代碼(C)

標籤：mystra   編程演算法   把字串轉換為整數   異常處理   c   

把字串轉換為整數 代碼(C)

本文地址: http://blog.csdn.net/caroline_wendy

題目: 寫一個函數StrToInt, 類比atoi的功能, 把字串轉換為整數.

需要考慮異常處理, 正負數, 還有Int的最大值(0x7FFFFFFF)和最小值(0x80000000)等情況.

代碼:

/* * main.cpp * *  Created on: 2014.7.12 *      Author: spike */#include <stdio.h>#include <stdlib.h>#include <string.h>#include <math.h>enum Status {kValid=0, kInvalid};int g_nStatus = kValid;long long StrToIntCore(const char* digit, bool minus) {long long num = 0;while (*digit != ‘\0‘) {if (*digit >= ‘0‘ && *digit <= ‘9‘) {int flag = minus ? -1 : 1;num = num*10 + flag*(*digit-‘0‘);if ((!minus && num>0x7FFFFFFF) || (minus && num <(signed int)0x80000000)) {num = 0;break;}digit++;} else {num = 0;break;}}if (*digit == ‘\0‘) {g_nStatus = kValid;}return num;}int StrToInt(const char* str) {g_nStatus = kInvalid;long long num = 0;if (str != NULL && *str != ‘\0‘) {bool minus = false;if (*str == ‘+‘)str++;else if (*str == ‘-‘) {str++;minus = true;}if (*str != ‘\0‘)num = StrToIntCore(str, minus);}return (int)num;}int main(void){char num[] = "-873141";int result = StrToInt(num);    printf("result = %d\n", result);    return 0;}

輸出:

result = -873141