点到线段的最短距离

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点到线段的最短距离

Java code

private double pointToLine(int x1, int y1, int x2, int y2, int x0,                int y0) {            double space = 0;            double a, b, c;            a = lineSpace(x1, y1, x2, y2);// 线段的长度            b = lineSpace(x1, y1, x0, y0);// (x1,y1)到点的距离            c = lineSpace(x2, y2, x0, y0);// (x2,y2)到点的距离            if (c <= 0.000001 || b <= 0.000001) {                space = 0;                return space;            }            if (a <= 0.000001) {                space = b;                return space;            }            if (c * c >= a * a + b * b) {                space = b;                return space;            }            if (b * b >= a * a + c * c) {                space = c;                return space;            }            double p = (a + b + c) / 2;// 半周长            double s = Math.sqrt(p * (p - a) * (p - b) * (p - c));// 海伦公式求面积            space = 2 * s / a;// 返回点到线的距离（利用三角形面积公式求高）            return space;        }        // 计算两点之间的距离        private double lineSpace(int x1, int y1, int x2, int y2) {            double lineLength = 0;            lineLength = Math.sqrt((x1 - x2) * (x1 - x2) + (y1 - y2)                    * (y1 - y2));            return lineLength;        }