UVA - 585 Triangles

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題意：求最大的三角形

思路：先初始化從左至右和從右至左的最大連續的‘-’，然後就是當奇數列的時候找頭向下的三角形，偶數的時候相反找

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>using namespace std;const int MAXN = 200;char  map[MAXN][MAXN];int Left[MAXN][MAXN], Right[MAXN][MAXN];int n;int main() {int cas = 1;while (scanf("%d", &n) != EOF && n) {memset(map, 0, sizeof(map));memset(Left, 0, sizeof(Left));memset(Right, 0, sizeof(Right));for (int i = 1; i <= n; i++)scanf("%s", map[i]+1);for (int i = 1; i <= n; i++) {int len = strlen(map[i]+1);for (int j = len; j >= 1; j--)if (map[i][j] == '-')Left[i][j] = Left[i][j+1] + 1;else Left[i][j] = 0;for (int j = 1; j <= len; j++)if (map[i][j] == '-')Right[i][j] = Right[i][j-1] + 1;else Right[i][j] = 0;}int ans = -1;for (int i = 1; i <= n; i++) {int len = strlen(map[i]+1);for (int j = 1; j <= len; j++)if (j&1) {int x = 0;while (i-x >= 1 && Left[i-x][j] >= 2*x+1)x++;ans = max(ans, x);}else {int x = 0;while (x+i <= n && Right[x+i][j] >= 2*x+1)x++;ans = max(ans, x);}}printf("Triangle #%d\nThe largest triangle area is %d.\n\n", cas++, ans*ans);}return 0;}