iOS 求笛卡尔积写法

求任意数组笛卡尔积 OC Swift 写法

NSMutableArray *arr = [NSMutableArray array];

[arr addObject:@[@"1",@"2",@"3"]];
[arr addObject:@[@"4",@"5",@"6"]];
[arr addObject:@[@"7",@"8",@"9"]];

NSMutableArray *result = [NSMutableArray array];

[self Descartes:arr result:result layer:0 curstring:@""];  

求这三个数组的笛卡尔积 ，结果应该是 有27个。

具体实现:

-(void)Descartes:(NSMutableArray <NSMutableArray <NSString *>*>*)dimvalue  result:(NSMutableArray <NSString *>*)result layer:(NSInteger)layer curstring:(NSString *)curstring{

if (layer < (dimvalue.count - 1)) {
    
    if (dimvalue[layer].count == 0) {
        [self Descartes:dimvalue result:result layer:layer + 1 curstring:curstring];
    }else{
        
        for (int i = 0; i < dimvalue[layer].count; i++) {
            
            [self Descartes:dimvalue result:result layer:layer + 1 curstring:[NSString stringWithFormat:@"%@%@",curstring,dimvalue[layer][i]]];
        }
    }
    
}else if (layer ==dimvalue.count - 1){
    
    if (dimvalue[layer].count == 0) {
        
        [result addObject:curstring];
    }else{
        
        for (int i = 0; i < dimvalue[layer].count; i++) {
            
            NSString *string = [NSString stringWithFormat:@"%@%@",curstring,dimvalue[layer][i]];
            [result addObject:string];
        }
        
    }
}

}

结果：

Paste_Image.png

Swift：

 var arr : [[String]] = [["1","2","3"],["4","5","6"],["7","8","9"]]
 var result : [String] = []

func Descartes(inout dimvalue : [[String]],inout result : [String],layer : NSInteger ,curstring : String){

if layer < dimvalue.count - 1 {
    
    if dimvalue[layer].count == 0 {
        
        Descartes(&dimvalue, result: &result, layer: layer, curstring: curstring)
    }else{
        
        for (index, _) in dimvalue[layer].enumerate() {
            
            Descartes(&dimvalue, result: &result, layer: layer + 1, curstring: curstring + dimvalue[layer][index])
        }
    }
    
}else if(layer == dimvalue.count - 1){
    
    if dimvalue[layer].count == 0 {
        
        result.append(curstring)
    }else{
        
        for (index, _) in dimvalue[layer].enumerate() {
            
            result.append(curstring + dimvalue[layer][index])
        }
        
    }
    
}

}

Descartes(&arr, result: &result, layer: 0, curstring: "")

print(result)