思路：先转化为二进制再转化为八进制

代码：

#include <stdio.h>#include <string.h>#define M 100005char s[M*4];char str[M];int ans[150005];int main(){	int n;	//char temp[6];	scanf("%d", &n);	while(n --){		scanf("%s", str+1);		memset(s, 0, sizeof(s));		int i, j, len = strlen(str+1)+1, temp;	//	printf("%d..\n", len);		for(i = 1; i < len; ++i){			if(str[i] >= '0'&&str[i] <= '9'){				temp = str[i] - '0';			}			else temp = 10+str[i]-'A';			j = i*4;			while(temp){				s[j] = temp%2+'0';				j--;				temp /= 2;			}			while(j > (i-1)*4){				s[j--] = '0';			}		}	//	printf("%s", &s[1]);		memset(ans, 0, sizeof(ans));		int tot = 0;		for(i = (len-1)*4; i-3 >= 0; i -= 3){			ans[tot++] = (s[i]-'0')+(s[i-1]-'0')*2+(s[i-2]-'0')*4;		}		temp = 1;		if(s[i] != '\0'){			++tot;			while(i > 0&&s[i]!='\0'){				ans[tot-1] += (s[i]-'0')*temp;				temp *= 2;				--i;			}		}		while(tot>0&&ans[tot] == 0) --tot;		for(i = tot; i >= 0; -- i) printf("%d", ans[i]);		puts("");		//		//for(i = ())	}	return 0;}

蓝桥杯 基础练习 十六进制转八进制 【字符串处理】