【HDU1272】小希的迷宫（并查集基础题）

仍旧裸敲并查集。有这两点注意：

1.输入 0 0 时候要输出YES

2.留心数组的初始化

 

#include <iostream>
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <numeric>
#include <algorithm>
#include <cctype>
#include <string>

using namespace std;

const int MAXN = 100001;

bool flag[MAXN];
int connectedList[MAXN];
bool isOk = true;
int nStart, nEnd;

void Init() {
    for (int i = 0; i < MAXN; ++i) {
        connectedList[i] = i;
        flag[i] = false;
    }
}

int getFather(int vetex) {
    int pos = vetex;
    while(pos != connectedList[pos]) {
        pos = connectedList[pos];
    }
    return pos;
}

int countListNum() {
    int count = 0;
    for (int i = 0; i < MAXN; ++i) {
        if (flag[i] == true) {
            if (getFather(i) == i) {
                ++count;
            }
        }
    }
    return count;
}

void process() {
    if( getFather(nStart) == getFather(nEnd)) {
        isOk = false;
        return;
    }
    if( getFather(nStart) == nStart && getFather(nEnd) == nEnd) {
        connectedList[nEnd] = nStart;
    } else if(getFather(nStart) == nStart) {
        connectedList[nStart] = getFather(nEnd);
    } else {
        connectedList[nEnd] = getFather(nStart);
    }
    flag[nStart] = true;
    flag[nEnd] = true;
}
int main() {
    while(cin >> nStart >> nEnd) {
        if(nStart == -1 && nEnd == -1) break;
        if(nStart || nEnd) {
            isOk = true;
            memset(flag, false , sizeof(flag));
            Init();
            process();

            while(cin >> nStart >> nEnd, nStart || nEnd) {
                if(isOk == true) {
                    process();
                }
            }

            if(isOk == true) {
                int count = 0;
                count = countListNum();
                if(count > 1) {
                    isOk = false;
                }
            }
        } else {
            isOk = true;
        }
        if(isOk == false) {
            cout << "No" << endl;
        } else {
            cout << "Yes" << endl;
        }
    }
    return 0;
}