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Flowcharts: Mermaid and Graphviz

Turns the same pseudocode into a Mermaid or Graphviz flowchart. Both engines share the same semantics; Graphviz prioritizes deterministic geometry.

The diagrams below are rendered directly by MkDocs from their Mermaid and Graphviz sources; no approximate static screenshots are used.

Complete example: mystery-number game

First, n is read as the upper bound. The program randomly chooses a target between 1 and n, then asks for guesses m. When the target is found, Break exits the loop.

Input n
target = randombetween(1, n)
m = target + 1
While m is not equal to target:
    Input m
    If m > target Then:
        Display "Too high!"
    Else If m < target Then:
        Display "Too low!"
    Else:
        Display "You won!"
        Break
    End
End

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3[/"Input n"/]
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    n4["target = randombetween(1, n)"]
    %% pseudocode-edge e1 n3 n4 normal
    n3 e1@--> n4
    %% pseudocode-sequence e1 n3 n4
    n5["m = target + 1"]
    %% pseudocode-edge e2 n4 n5 normal
    n4 e2@--> n5
    %% pseudocode-sequence e2 n4 n5
    n6{"While m is not equal to target ?"}
    %% pseudocode-edge e3 n5 n6 normal
    n5 e3@--> n6
    %% pseudocode-sequence e3 n5 n6
    subgraph loop1_body[" "]
        direction TB
    n7[/"Input m"/]
    n8{"m #62; target ?"}
    %% pseudocode-edge e4 n7 n8 normal
    n7 e4@--> n8
    %% pseudocode-sequence e4 n7 n8
    n9[/"Display 'Too high!'"/]
    %% pseudocode-edge e5 n8 n9 branch
    n8 e5@-->|"Yes"| n9
    n10{"m #60; target ?"}
    %% pseudocode-edge e6 n8 n10 branch
    n8 e6@-->|"No"| n10
    n11[/"Display 'Too low!'"/]
    %% pseudocode-edge e7 n10 n11 branch
    n10 e7@-->|"Yes"| n11
    n12[/"Display 'You won!'"/]
    %% pseudocode-edge e8 n10 n12 branch
    n10 e8@-->|"No"| n12
    n13["Break"]
    %% pseudocode-edge e9 n12 n13 normal
    n12 e9@--> n13
    %% pseudocode-sequence e9 n12 n13
    n14((" ")):::pseudocodeGhost
    %% pseudocode-edge e10 n9 n14 normal
    n9 e10@--- n14
    %% pseudocode-sequence e10 n9 n14
    %% pseudocode-edge e11 n11 n14 normal
    n11 e11@--- n14
    %% pseudocode-sequence e11 n11 n14
    end
    style loop1_body fill:none,stroke:none
    %% pseudocode-edge e12 n6 n7 branch
    n6 e12@-->|"Yes"| n7
    %% pseudocode-loop-continue e12 n6 n7
    %% pseudocode-edge e13 n14 n6 loop_back
    n14 e13@--> n6
    %% pseudocode-loop-back e13 n14 n6
    %% pseudocode-edge e14 n6 n2 branch
    n6 e14@-->|"No"| n2
    %% pseudocode-loop-exit e14 n6 n2
    %% pseudocode-edge e15 n13 n2 normal
    n13 e15@--> n2
    %% pseudocode-sequence e15 n13 n2
    classDef pseudocodeGhost fill:transparent,stroke:transparent,color:transparent;

pseudocoden1:s->n3:nn3:s->n4:nn4:s->n5:nn5:s->n6:nn6:s->n7:nYesn6:e->__exit_top_3:wNon7:s->n8:nn8:s->n9:nYesn8:e->n10:nNon9:s->n14:nn10:s->n11:nYesn10:e->n12:nNon11:s->n14:nn12:s->n13:nn13:s->n2:nn14:w->__return_bottom_1:e__return_bottom_1:n->__return_top_2:s__return_top_2:e->n6:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n2:en1Startn2Endn3Input nn4target = randombetween(1, n)n5m = target + 1n6While m is not equal to target ?n7Input mn8m > target ?n9Display "Too high!"n10m < target ?n11Display "Too low!"n12Display "You won!"n13Break

Main programming structures

The following examples isolate the most common control structures so their Mermaid and Graphviz renderings can be compared quickly.

Condition: If … Then … Else …

x = 5
If x > 0 Then:
    Display "positive"
Else:
    Display "zero or negative"
End

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3["x = 5"]
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    n4{"x #62; 0 ?"}
    %% pseudocode-edge e1 n3 n4 normal
    n3 e1@--> n4
    %% pseudocode-sequence e1 n3 n4
    n5[/"Display 'positive'"/]
    %% pseudocode-edge e2 n4 n5 branch
    n4 e2@-->|"Yes"| n5
    n6[/"Display 'zero or negative'"/]
    %% pseudocode-edge e3 n4 n6 branch
    n4 e3@-->|"No"| n6
    %% pseudocode-edge e4 n5 n2 normal
    n5 e4@--> n2
    %% pseudocode-sequence e4 n5 n2
    %% pseudocode-edge e5 n6 n2 normal
    n6 e5@--> n2
    %% pseudocode-sequence e5 n6 n2

pseudocoden1:s->n3:nn3:s->n4:nn4:s->n5:nYesn4:e->n6:nNon5:s->n2:nn6:s->n2:nn1Startn2Endn3x = 5n4x > 0 ?n5Display "positive"n6Display "zero or negative"

Loop: For … from … to …

total = 0
For i from 1 to 5:
    total = total + i
End
Display total

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3["total = 0"]
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    n4{"For i from 1 to 5"}
    %% pseudocode-edge e1 n3 n4 normal
    n3 e1@--> n4
    %% pseudocode-sequence e1 n3 n4
    subgraph loop1_body[" "]
        direction TB
    n5["total = total + i"]
    end
    style loop1_body fill:none,stroke:none
    %% pseudocode-edge e2 n4 n5 branch
    n4 e2@-->|"Yes"| n5
    %% pseudocode-loop-continue e2 n4 n5
    %% pseudocode-edge e3 n5 n4 loop_back
    n5 e3@-->|"(i = i + 1)"| n4
    %% pseudocode-loop-back e3 n5 n4
    n6[/"Display total"/]
    %% pseudocode-edge e4 n4 n6 branch
    n4 e4@-->|"No"| n6
    %% pseudocode-loop-exit e4 n4 n6
    %% pseudocode-edge e5 n6 n2 normal
    n6 e5@--> n2
    %% pseudocode-sequence e5 n6 n2

pseudocoden1:s->n3:nn3:s->n4:nn4:s->n5:nYesn4:e->__exit_top_3:wNon5:w->__return_bottom_1:e(i = i + 1)n6:s->n2:n__return_bottom_1:n->__return_top_2:s__return_top_2:e->n4:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n6:en1Startn2Endn3total = 0n4For i from 1 to 5n5total = total + in6Display total

Loop: For … from … to … with a step …

For i from 0 to 10 with a step of 2:
    Display i
End

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3{"For i from 0 to 10 with a step of 2"}
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    subgraph loop1_body[" "]
        direction TB
    n4[/"Display i"/]
    end
    style loop1_body fill:none,stroke:none
    %% pseudocode-edge e1 n3 n4 branch
    n3 e1@-->|"Yes"| n4
    %% pseudocode-loop-continue e1 n3 n4
    %% pseudocode-edge e2 n4 n3 loop_back
    n4 e2@-->|"(i = i + 2)"| n3
    %% pseudocode-loop-back e2 n4 n3
    %% pseudocode-edge e3 n3 n2 branch
    n3 e3@-->|"No"| n2
    %% pseudocode-loop-exit e3 n3 n2

pseudocoden1:s->n3:nn3:s->n4:nYesn3:e->__exit_top_3:wNon4:w->__return_bottom_1:e(i = i + 2)__return_bottom_1:n->__return_top_2:s__return_top_2:e->n3:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n2:en1Startn2Endn3For i from 0 to 10 with a step of 2n4Display i

Loop: For … In …

For c In "Hello":
    Display c
End

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3{"For c In 'Hello'"}
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    subgraph loop1_body[" "]
        direction TB
    n4[/"Display c"/]
    end
    style loop1_body fill:none,stroke:none
    %% pseudocode-edge e1 n3 n4 branch
    n3 e1@-->|"Yes"| n4
    %% pseudocode-loop-continue e1 n3 n4
    %% pseudocode-edge e2 n4 n3 loop_back
    n4 e2@--> n3
    %% pseudocode-loop-back e2 n4 n3
    %% pseudocode-edge e3 n3 n2 branch
    n3 e3@-->|"No"| n2
    %% pseudocode-loop-exit e3 n3 n2

pseudocoden1:s->n3:nn3:s->n4:nYesn3:e->__exit_top_3:wNon4:w->__return_bottom_1:e__return_bottom_1:n->__return_top_2:s__return_top_2:e->n3:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n2:en1Startn2Endn3For c In "Hello"n4Display c

Loop: While …

i = 0
While i < 3:
    Display i
    i = i + 1
End

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3["i = 0"]
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    n4{"While i #60; 3 ?"}
    %% pseudocode-edge e1 n3 n4 normal
    n3 e1@--> n4
    %% pseudocode-sequence e1 n3 n4
    subgraph loop1_body[" "]
        direction TB
    n5[/"Display i"/]
    n6["i = i + 1"]
    %% pseudocode-edge e2 n5 n6 normal
    n5 e2@--> n6
    %% pseudocode-sequence e2 n5 n6
    end
    style loop1_body fill:none,stroke:none
    %% pseudocode-edge e3 n4 n5 branch
    n4 e3@-->|"Yes"| n5
    %% pseudocode-loop-continue e3 n4 n5
    %% pseudocode-edge e4 n6 n4 loop_back
    n6 e4@--> n4
    %% pseudocode-loop-back e4 n6 n4
    %% pseudocode-edge e5 n4 n2 branch
    n4 e5@-->|"No"| n2
    %% pseudocode-loop-exit e5 n4 n2

pseudocoden1:s->n3:nn3:s->n4:nn4:s->n5:nYesn4:e->__exit_top_3:wNon5:s->n6:nn6:w->__return_bottom_1:e__return_bottom_1:n->__return_top_2:s__return_top_2:e->n4:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n2:en1Startn2Endn3i = 0n4While i < 3 ?n5Display in6i = i + 1

Loop: Repeat … times

Repeat 3 times:
    Display "Hello"
End

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3{"Repeat 3 times"}
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    subgraph loop1_body[" "]
        direction TB
    n4[/"Display 'Hello'"/]
    end
    style loop1_body fill:none,stroke:none
    %% pseudocode-edge e1 n3 n4 branch
    n3 e1@-->|"Yes"| n4
    %% pseudocode-loop-continue e1 n3 n4
    %% pseudocode-edge e2 n4 n3 loop_back
    n4 e2@--> n3
    %% pseudocode-loop-back e2 n4 n3
    %% pseudocode-edge e3 n3 n2 branch
    n3 e3@-->|"No"| n2
    %% pseudocode-loop-exit e3 n3 n2

pseudocoden1:s->n3:nn3:s->n4:nYesn3:e->__exit_top_3:wNon4:w->__return_bottom_1:e__return_bottom_1:n->__return_top_2:s__return_top_2:e->n3:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n2:en1Startn2Endn3Repeat 3 timesn4Display "Hello"

Loop: Repeat … Until …

i = 0
Repeat:
    Display i
    i = i + 1
Until i >= 3

%%{init: {"flowchart":{"curve":"basis","nodeSpacing":55,"rankSpacing":72,"htmlLabels":false},"layout":"elk","look":"classic","elk":{"preset":"modelOrder","nodePlacementStrategy":"LINEAR_SEGMENTS","nodePlacementAlignment":"NONE","layeringStrategy":"NETWORK_SIMPLEX","cycleBreakingStrategy":"MODEL_ORDER","considerModelOrder":"NODES_AND_EDGES","forceNodeModelOrder":true,"keepEntryNodeOnTop":true,"straightenEdges":true,"lineHops":false,"mergeEdges":false},"htmlLabels":false}}%%
%% pseudocode-layout-profile: validated-loop-attached-edges-v22
flowchart TD
    n1(["Start"])
    n2(["End"])
    n3["i = 0"]
    %% pseudocode-edge e0 n1 n3 normal
    n1 e0@--> n3
    %% pseudocode-sequence e0 n1 n3
    subgraph loop1[" "]
        direction TB
        subgraph loop1_body[" "]
            direction TB
    n4[/"Display i"/]
    n5["i = i + 1"]
    %% pseudocode-edge e1 n4 n5 normal
    n4 e1@--> n5
    %% pseudocode-sequence e1 n4 n5
        end
    style loop1_body fill:none,stroke:none
        subgraph loop1_condition[" "]
            direction TB
    n6{"i #62;= 3 ?"}
        end
    style loop1_condition fill:none,stroke:none
    %% pseudocode-edge e2 n5 n6 normal
    n5 e2@--> n6
    %% pseudocode-sequence e2 n5 n6
    end
    style loop1 fill:none,stroke:none
    %% pseudocode-edge e3 n3 n4 normal
    n3 e3@--> n4
    %% pseudocode-sequence e3 n3 n4
    %% pseudocode-edge e4 n6 n4 loop_back
    n6 e4@-->|"No"| n4
    %% pseudocode-loop-back e4 n6 n4
    %% pseudocode-edge e5 n6 n2 branch
    n6 e5@-->|"Yes"| n2
    %% pseudocode-loop-exit e5 n6 n2

pseudocoden1:s->n3:nn3:s->n4:nn4:s->n5:nn5:s->n6:nn6:w->__return_bottom_1:eNon6:e->__exit_top_3:wYes__return_bottom_1:n->__return_top_2:s__return_top_2:e->n4:w__exit_top_3:s->__exit_bottom_4:n__exit_bottom_4:w->n2:en1Startn2Endn3i = 0n4Display in5i = i + 1n6i >= 3 ?