HDU 4164 contour Tracing

Question:

The contour tracking algorithm provides a way to ensure that all images with contours do not have holes in the image. The pixels smaller than 5 are used to calculate the noise and sort the outlines of all images.

Ideas:

Just simulate the question logic.

First, we need BFs to determine which image is a piece and discard the noise. Then, we need to implement the contour tracking algorithm provided by the question and finally output the contour sorting.

Code:

#include<cstdio>#include<iostream>#include<cstring>#include<string>#include<algorithm>#include<map>#include<set>#include<vector>#include<queue>#include<cstdlib>#include<ctime>#include<cmath>#include<bitset>using namespace std;#define N 210#define inf 50000000int dir[8][2] = { { 0, 1 }, { 1, 1 }, { 1, 0 }, { 1, -1 }, { 0, -1 },        { -1, -1 }, { -1, 0 }, { -1, 1 } };int T = 1, n, m, idx, tot;int maz[N][N], done[N * N], ans[N * N];char Map[N][N];struct position {    int x, y;} u, v, qu[N * N];void bfs(int x, int y) {    maz[x][y] = idx;    Map[x][y] = '0';    u.x = x;    u.y = y;    int l = 0, r = 1;    qu[0] = u;    while (l < r) {        u = qu[l++];        for (int i = 0; i < 8; i++) {            v.x = u.x + dir[i][0];            v.y = u.y + dir[i][1];            if (v.x >= 1 && v.x <= n && v.y >= 1 && v.y <= m                    && Map[v.x][v.y] == '1') {                maz[v.x][v.y] = idx;                Map[v.x][v.y] = '0';                qu[r++] = v;            }        }    }    if (r < 5)        done[idx] = 1;}void solve(int x, int y) {    u.x = x;    u.y = y;    int i = 1, to = 6;    qu[0] = u;    for (;;) {        int flag = 0;        for (int j = to; j != to || !flag; j = (j + 1) % 8) {            if (j == to)                flag = 1;            v.x = u.x + dir[j][0];            v.y = u.y + dir[j][1];            if (v.x >= 1 && v.x <= n && v.y >= 1 && v.y <= m                    && maz[v.x][v.y] == maz[x][y]) {                u.x = u.x + dir[(j + 7) % 8][0];                u.y = u.y + dir[(j + 7) % 8][1];                for (j = 0; j < 8; j++) {                    if (v.x + dir[j][0] == u.x && v.y + dir[j][1] == u.y) {                        to = j;                        break;                    }                }                qu[i++] = v;                u = v;                if (i >= 4 && qu[0].x == qu[i - 2].x && qu[0].y == qu[i - 2].y                        && qu[1].x == qu[i - 1].x && qu[1].y == qu[i - 1].y) {                    ans[tot++] = i - 2;                    return;                }                break;            }        }    }}int main() {    while (~scanf("%d%d", &n, &m)) {        if (!n && !m)            break;        for (int i = 1; i <= n; i++)            scanf("%s", Map[i] + 1);        idx = 0;        memset(maz, 0, sizeof(maz));        for (int i = 1; i <= n; i++) {            for (int j = 1; j <= m; j++) {                if (Map[i][j] == '1') {                    idx++;                    done[idx] = 0;                    bfs(i, j);                }            }        }//        for (int i = 1; i <= n; i++) {//            for (int j = 1; j <= m; j++) {//                printf("%d", maz[i][j]);//            }//            printf("\n");//        }        tot = 0;        for (int i = 1; i <= n; i++) {            for (int j = 1; j <= m; j++) {                if (maz[i][j] && !done[maz[i][j]]) {                    done[maz[i][j]] = 1;                    solve(i, j);//                    printf("%d %d\n", maz[i][j], ans[tot - 1]);                }            }        }        printf("Case %d\n", T++);        if (tot) {            sort(ans, ans + tot);            for (int i = 0; i < tot; i++)                printf("%d%s", ans[i], (i == tot - 1) ? "\n" : " ");        } else            printf("no objects found\n");    }    return 0;}

HDU 4164 contour Tracing