利用中序和后序构建二叉树然后进行dfs搜索，两步可以同时进行，另外这道题目输入处理也有点麻烦，参考了一些大神的代码，自己重写因为一个值每次case之后未初始化悲剧的RE了好多次。
查了下 runtime error的可能大概有：
Runtime Error(ARRAY_BOUNDS_EXCEEDED) // array bounds exceed 数组越界
Runtime Error(DIVIDE_BY_ZERO) //divisor is nil 除零Runtime Error(ACCESS_VIOLATION) //illegal memory access 非法内存读取Runtime Error(STACK_OVERFLOW) //stack overflow 系统栈过载
#includeint in[10010];int post[10010];int minSum;int res;int findIndex(int key, int*array, int n) { int i; for (i = 0; i < n; i++) { if (array[i] == key) return i; } return -1;}void dfs(int n, int*in, int*post, int sum) { if (n <= 0) return; int root = post[n - 1]; if (n == 1) { int tmpSum = sum + root; if (tmpSum < minSum) { minSum = tmpSum; res = root; } else if (tmpSum == minSum) res = res < root ? res : root; return; } int index = findIndex(post[n - 1], in, n); dfs(index, in, post, sum + root); dfs(n - index - 1, in + index + 1, post + index, sum + root);}int main() { /* setbuf(stdout,NULL);*/ char ch; int i, n; while (scanf("%d%c", &in[0], &ch) != EOF) { minSum = 0x7fffffff; res = 0x7fffffff; if (ch == '\n') { scanf("%d", &post[0]); printf("%d\n", post[0]); continue; } n = 1; while (scanf("%d%c", &in[n++], &ch)) { if (ch == '\n') break; } for (i = 0; i < n; i++) scanf("%d", &post[i]); dfs(n, in, post, 0); printf("%d\n", res); } return 0;}