UVA - 11039 Building designing

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题目大意：搭建楼层，下一层比上一层大且颜色交替（即正负交替），问最多能搭几层

解题思路：正负数分别存于两个数组，轮流在两个数组取合适的数。模拟过程好复杂而且 WA 好几次。

#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>using namespace std;int neg[1000000], pos[1000000];int ans1[1000000], ans2[1000000];int t1, t2, tag, tot1, tot2;int cmp(const void*a, const void*b) {    return *(int*)a-*(int*)b;}int solve(int ans[]) {    int i;    for (i = 1; t1 <= tot1 && t2 <= tot2; i++) {        if (tag == 1) {             tag = 2;            while (t2 < tot2 && neg[t2] < ans[i-1]) t2++;            if (neg[t2] > ans[i-1]) ans[i] = neg[t2++];            else break;             }        else{            tag = 1;            while (t1 < tot1 && pos[t1] < ans[i-1]) t1++;            if (pos[t1] > ans[i-1]) ans[i] = pos[t1++];            else break;        }    }    return i;}int main() {    int p, n, t;    scanf("%d", &p);    while (p--) {        memset(ans1, 0, sizeof(ans1));        memset(ans2, 0, sizeof(ans2));        memset(pos, 0, sizeof(pos));        memset(neg, 0, sizeof(neg));        scanf("%d", &n);         tot1 = 0, tot2 = 0;        while (n--) {            scanf("%d", &t);            if (t > 0) pos[tot1++] = t;            else neg[tot2++] = -t;        }        qsort(pos, tot1, sizeof(int), cmp);        qsort(neg, tot2, sizeof(int), cmp);/*for (int i = 0; i < tot1; i++)    cout<<pos[i]<<" ";cout<<endl;for (int i = 0; i < tot2; i++)    cout<<neg[i]<<" ";cout<<endl;*/        t1 = t2 = 0;        ans1[0] = pos[t1++];        tag = 1;        int m = solve(ans1);        t1 = t2 = 0;        ans2[0] = neg[t2++];        tag = 2;        int n = solve(ans2);/*for (int j = 0; j < m; j++)    cout<<ans1[j]<<" ";cout<<endl;for (int j = 0; j < n; j++)    cout<<ans2[j]<<" ";cout<<endl;*/        printf("%d\n", max(m, n));    }    return 0;}

以下是大神的思路：绝对值排序，相邻两个数相乘小于零说明正负交替，注意相乘可能会爆，要用 long long。比上面自己想的简单的多qwq。

#include<iostream>#include<cstdio>#include<cstdlib>#include<cstring>#include<cmath>#include<algorithm>using namespace std;long long flor[600000];bool cmp(int a, int b) {    return abs(a)>abs(b);}int main() {    int p, n;    scanf("%d", &p);    while (p--) {        scanf("%d", &n);        for (int i = 0; i < n; i++)            scanf("%lld", &flor[i]);        sort(flor, flor+n, cmp);        int cnt = 1;        for (int i = 1; i < n; i++)            if (flor[i] * flor[i-1] < 0)                cnt++;        printf("%d\n", cnt);    }    return 0;}

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