699UVa"\b"的问题

//printf(" \b");

添上这一句后WA。\b无效？

#include<stdio.h>#include<string.h>const int max = 200;int res[max];void tree(int pos);int main(){//freopen("input.txt","r",stdin);int numcase = 1;int root;while(scanf("%d", &root)==1 && root!=-1){memset(res, 0, sizeof(res) );int pos = max/2;res[pos] = root;tree(pos-1);tree(pos+1);printf("Case %d:\n",numcase++);int i;for(i = 0; i < max && !res[i];i++);printf("%d",res[i]);for(i++; i < max;i++)if(res[i]) printf(" %d",res[i]);//printf(" \b");printf("\n\n");}}void tree(int pos){int num;scanf("%d", &num);if(num == -1) return;res[pos] += num;tree(pos-1);tree(pos+1);}