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  • luogu P1663 山

    题目链接

    luogu P1663 山

    题解

    只需要求出下凸包的最低点就好了
    显然是由两个斜率相反的直线相交来的
    盼下最低点为直线的情况

    代码

    #include<cstdio> 
    #include<iostream> 
    #include<algorithm> 
    inline int read() { 
        int x = 0,f = 1; 
        char c = getchar(); 
        while(c < '0' || c > '9')c = getchar(); 
        while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar(); 
        return x * f; 
    } 
    const int maxn = 10007;  
    int n; 
    double x[maxn],y[maxn]; 
    double k[maxn],b[maxn]; 
    int main() { 
        n = read(); 
        scanf("%lf%lf",&x[1],&y[1]); 
        for(int i = 2;i <= n;++ i) { 
            scanf("%lf%lf",x + i,y + i); 
            k[i] = (y[i] - y[i - 1]) / (x[i] - x[i - 1]); 
            b[i] = y[i] - k[i] * x[i]; 
        } 
        double ans = 0.0; 
        for(int i = 1;i <= n;++ i) 
            for(int j = i + 1;j <= n;++ j) {
                if((k[j] > 0 && k[i] < 0) || (k[i] > 0 && k[j] < 0))  { 
                    double X = (b[i] - b[j]) / (k[j] - k[i]); 
                    if(X * k[i] + b[i] > ans) ans = X * k[i] + b[i]; 
                }  
                else if(!k[j] && !k[i] && b[i] == b[j])  
                    if(ans < b[i]) ans = b[i]; 
            } 
        printf("%.7lf",ans); 
        return 0; 
    } 
    
    
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  • 原文地址:https://www.cnblogs.com/sssy/p/9452782.html
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