C/C++ ip地址与int类型的转换实例详解
前言
最近看道一个面试题目，大体意思就是将ip地址，例如“192.168.1.116”转换成int类型，同时还能在转换回去
思路
ip地址转int类型，例如ip为“192.168.1.116”,相当于“.“将ip地址分为了4部分，各部分对应的权值为256^3, 256^2, 256, 1,相成即可
int类型转ip地址，思路类似，除以权值即可，但是有部分字符串的操作
实现代码
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#include <stdio.h> #include <stdlib.h> #include <string.h> #include <math.h> #define LEN 16 typedef unsigned int uint; /** * 字符串转整形 */uint ipTint(char *ipstr) { if (ipstr == NULL) return 0; char *token; uint i = 3, total = 0, cur; token = strtok(ipstr, "."); while (token != NULL) { cur = atoi(token); if (cur >= 0 && cur <= 255) { total += cur * pow(256, i); } i --; token = strtok(NULL, "."); } return total; } /** * 逆置字符串 */void swapStr(char *str, int begin, int end) { int i, j; for (i = begin, j = end; i <= j; i ++, j --) { if (str[i] != str[j]) { str[i] = str[i] ^ str[j]; str[j] = str[i] ^ str[j]; str[i] = str[i] ^ str[j]; } } } /** * 整形转ip字符串 */char* ipTstr(uint ipint) { char *new = (char *)malloc(LEN); memset(new, '\0', LEN); new[0] = '.'; char token[4]; int bt, ed, len, cur; while (ipint) { cur = ipint % 256; sprintf(token, "%d", cur); strcat(new, token); ipint /= 256; if (ipint) strcat(new, "."); } len = strlen(new); swapStr(new, 0, len - 1); for (bt = ed = 0; ed < len;) { while (ed < len && new[ed] != '.') { ed ++; } swapStr(new, bt, ed - 1); ed += 1; bt = ed; } new[len - 1] = '\0'; return new; } int main(void) { char ipstr[LEN], *new; uint ipint; while (scanf("%s", ipstr) != EOF) { ipint = ipTint(ipstr); printf("%u\n", ipint); new = ipTstr(ipint); printf("%s\n", new); } return 0; } |
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