UVA - 1419 Ugly Windows

题目大意：给出一张图，模仿电脑窗口，问有哪些窗口未被其他窗口覆盖。

解题思路：水题。按顺序枚举字母，在地图中找到第一个该字母的点，向右向下搜索。最后看能不能构成右下角。唯一要注意的是，窗口可能会嵌套tc。要判断窗口中有没有其他字母。

#include <cstdio>

int main() {
    char s[110][110];
    int n, m;
    while (scanf("%d%d", &n, &m) && n + m) {
        int ans[40] = {0};
        for (int i = 0; i < n; i++)
            scanf("%s", s[i]);

        for (int i = 0; i < n; i++)
            for (int j = 0; j < m; j++)
                if (s[i][j] != '.') {
                    int left = 0, right = 0, up = 0, down = 0, flag = 1;
                    char C = s[i][j];
                    for (int k = j; k < m && s[i][k] == C; k++)
                        up++;
                    for (int k = i; k < n && s[k][j] == C; k++)
                        left++;
                    for (int k = i; k < n && s[k][j+up-1] == C; k++)
                        right++;
                    for (int k = j; k < m && s[i+left-1][k] == C; k++)
                        down++;

                    for (int p = i + 1; p < i + left - 1; p++)
                        for (int q = j + 1; q < j + up - 1; q++) if (s[p][q] != '.') flag = 0; if (left == right && up == down && left > 2 && up > 2 && flag)
                        ans[C-'A'] = 1;
                }

        for (int i = 0; i < 26; i++)
            if (ans[i])
                printf("%c", i + 'A');
        printf("\n");

    }
    return 0;
}