【HDOJ】2266 How Many Equations Can You Find

简单DFS。

#include <cstdio>
#include <cstring>

#define MAXN 15

char str[MAXN];
__int64 x;
int n;

void dfs(int s, __int64 v) {
    int i;
    __int64 tmp = 0;
    if (str[s] == '') {
        if (v == x)
            ++n;
        return ;
    }

    for (i=s; str[i]; ++i) {
        tmp = 10*tmp + str[i] - '0';
        dfs(i+1, v+tmp);
        if (s)
            dfs(i+1, v-tmp);
    }
}

int main() {

    while (scanf("%s %I64d", str, &x) != EOF) {
        n = 0;
        dfs(0, 0);
        printf("%d
", n);
    }

    return 0;
}