USACO NameThatNumber

　　就是给你一串数字， 每个数字可以翻译成三个字母， 有一个奶牛姓名表， 输入一串数字然后求出数字可以表示的姓名看看姓名表里面有没有， 有的话输出来，暴力+二分查找即可：

/*
    ID: m1500293
    LANG: C++
    PROG: namenum
*/
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

char validname[5000][15];
int validnum;

void getname()
{
    validnum = 0;
    FILE *dict = fopen("dict.txt", "r");
    while(!feof(dict))
    {
        fscanf(dict, "%s", validname[validnum++]);
    }
}

char strr[12][5] = {"000", "000", "ABC", "DEF", "GHI", "JKL", "MNO",
                   "PRS", "TUV", "WXY" };

int check(char str[])
{
    int res = -1;
    int l=0, r=validnum-1;
    while(l <= r)
    {
        int mid = (l+r)/2;
        int tp = strcmp(validname[mid], str);
        if(tp == 0)
        {
            res = mid;
            break;
        }
        else if(tp > 0) r = mid-1;
        else l = mid + 1;
    }
    if(res == -1) return 0;
    else return 1;
}

char input[15];
int len;
bool flog;
void dfs(int dept, char str[])
{
    //printf("%d\n", dept);
    if(dept == len)
    {
        str[dept] = ‘\0‘;
    //    printf("%s\n", str);
        if(check(str))
        {
            printf("%s\n", str);
            flog = true;
        }
        return ;
    }
    for(int i=0; i<3; i++)
    {
        str[dept] = strr[input[dept]-‘0‘][i];
        dfs(dept+1, str);
    }
}

int main()
{
    freopen("namenum.in", "r", stdin);
    freopen("namenum.out", "w", stdout);
    getname();
    while(scanf("%s", input)!=EOF)
    {
        char str[20];
        flog = false;
        len = strlen(input);
        dfs(0, str);
        if(!flog) printf("NONE\n");
    }
    return 0;
}