AcWing 1106. 山峰和山谷

题目链接AcWing 1106. 山峰和山谷

经典Flood Fill 用bfs做

#include <iostream>
#include <algorithm>
#include <cstring>
#define x first
#define y second

using namespace std;

typedef pair<int, int> PII;

const int N = 1010;

int n;
int h[N][N];
bool st[N][N];
PII q[N * N];

void bfs(int sx, int sy, bool &has_higher, bool &has_lower)
{
    st[sx][sy] = true;
    int hh = 0, tt = 0;
    q[0] = {sx, sy};
    while(hh <= tt)
    {
        PII t = q[hh ++];
        for(int i = t.x - 1; i <= t.x + 1; i ++)
            for(int j = t.y - 1; j <= t.y + 1; j ++)
            {
                if(i == t.x && j == t.y) continue;
                if(i >= n || i < 0 || j < 0 || j >= n) continue;
                if(h[i][j] != h[t.x][t.y])
                {
                    if(h[i][j] > h[t.x][t.y]) has_higher = true;
                    else has_lower = true;
                }
                else if(!st[i][j])
                {
                    q[++ tt] = {i, j};
                    st[i][j] = true;
                }
            }
    }
}

int main()
{
    cin >> n;
    for(int i = 0; i < n; i ++)
        for(int j = 0; j < n; j ++)
            scanf("%d", &h[i][j]);
    int peak = 0, valley = 0;
    for(int i = 0; i < n; i ++)
        for(int j = 0; j < n; j ++)
            if(!st[i][j])
            {
                bool has_higher = false, has_lower = false;
                bfs(i, j, has_higher, has_lower);
                if(!has_higher) peak ++;     //周围没有比他更高的 山峰+1
                if(!has_lower) valley ++;   //周围没有比他更矮的 山谷+1
            }
    cout << peak << ' ' << valley << endl;
    return 0;
}