编程算法

把字符串转换为整数 代码(C)

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

题目: 写一个函数StrToInt, 模拟atoi的功能, 把字符串转换为整数.

须要考虑异常处理, 正负数, 还有Int的最大值(0x7FFFFFFF)和最小值(0x80000000)等情况.

代码:

/*
 * 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 != '') {
		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 == '') {
		g_nStatus = kValid;
	}
	return num;
}

int StrToInt(const char* str) {
	g_nStatus = kInvalid;
	long long num = 0;
	if (str != NULL && *str != '') {
		bool minus = false;
		if (*str == '+')
			str++;
		else if (*str == '-') {
			str++;
			minus = true;
		}

		if (*str != '')
			num = StrToIntCore(str, minus);
	}

	return (int)num;
}

int main(void)
{
	char num[] = "-873141";
	int result = StrToInt(num);
    printf("result = %d
", result);
    return 0;
}

输出:

result = -873141