Uva 1587：Box

题目传送门：https://cn.vjudge.net/problem/UVA-1587

#include <stdio.h>struct p{    int w, h;}ps[6], cps[3];bool isSame(int i, int j){    return (ps[i].w == ps[j].w && ps[i].h == ps[j].h)        || (ps[i].w == ps[j].h && ps[i].h == ps[j].w);}bool dfs(int a, int b, int depth) // 旋转拼接三个板子{    if (2 == depth) {        if (a == cps[depth].w && b == cps[depth].h) return true;        if (a == cps[depth].h && b == cps[depth].w) return true;        return false;    }    if (cps[depth].w == a)        if (dfs(cps[depth].h, b, depth+1))            return true;    if (cps[depth].h == a)        if (dfs(cps[depth].w, b, depth+1))            return true;    return false;}int main(){    while (2 == scanf("%d%d", &ps[0].w, &ps[0].h)) {        bool used[6] = {false}; int ct = 0;        for (int i = 1; i < 6; ++i)            scanf("%d%d", &ps[i].w, &ps[i].h);        for (int i = 0, j; i < 6; ++i) { // 首先确定是否有三对相同的板子            if (used[i]) continue;            for (j = i + 1; j < 6; ++j) {                if (used[j]) continue;                if (isSame(i, j)) {                    used[i] = used[j] = true;                    cps[ct++] = ps[i]; // 记住三组板子                    break;                }            }            if (6 == j)                break;        }        //printf("ct = %d\n", ct);        if (ct < 3) { printf("IMPOSSIBLE\n"); continue; }        if (dfs(cps[0].w, cps[0].h, 1) || dfs(cps[0].h, cps[0].w, 1)) // 旋转拼接三个板子            printf("POSSIBLE\n");        else            printf("IMPOSSIBLE\n");    }    return 0;}